Top 46 Beginner Questions About The Aquarium


As a beginner, you might have questions regarding your new aquarium.

This guide below covers the top 46 beginner questions you might need answers to when you decide to get an aquarium.

Beginner Questions: UV Clarifiers

Before and after using UV clarifier in the aquarium

1. When does a UV clarifier make sense?

The use of a UV clarifier makes sense

  • to help treat diseases caused by bacteria or parasites floating in the water .
  • to combat floating algae .
  • to combat bacterial water cloudiness.
  • in breeding facilities.
  • in sales systems.

Advantages of UV clarifiers are

  • clear water.
  • less bacterial contamination of the water.

Disadvantages of UV clarifiers are

  • the dampening of drug effects
  • the decomposition of plant fertilizers. It has to be re-fertilized more often.

Care must be taken when purchasing UV clarifiers

  • the largest possible contact surface of the UV lamp with the water.
  • the possibility of easy cleaning.
  • easy dismantling.
  • widely available and reliable burner lamps, e.g. from Philips. These look similar to energy-saving lamps with a base.

The strength of UV clarifiers is determined by the wattage. Depending on the aquarium size, a different wattage is required to achieve a noticeable effect. UV clarifiers for pond systems are also suitable for larger aquariums.

Depending on the wattage and quality, a UV clarifier costs between 100 and 300 euros.

Beginner questions: Fish in the aquarium

Top 10 Aquarium Fish For Beginners! Your First Aquarium!

2. How many fish can you keep in an aquarium?

The exact number of fish that can be kept in an aquarium depends on the type of fish you want.

As a rule of thumb for beginners, we recommend calculating at least 2 liters of water for one centimeter of fish.

The amount of water available in the aquarium is the content of the aquarium minus the pane thickness and minus the decoration.

The size of the later adult fish is calculated as the fish size. In addition, the requirements and behavior of the fish must be observed.

Some species of fish, e.g. Armored catfish and many tetra only feel comfortable in groups and at least 5 to 7 animals of these species should be kept together.

3. How does a typical beginner aquarium look like?

In a typical beginner aquarium with approx. 50 liters of water, a maximum of 5 fish of approx. 5 cm in size can be kept according to the rule of thumb. If dwarf cichlids  are to be kept, however, a maximum of one male and one female can be kept.

The  appropriate size tetra can be kept in a small school of 5 to 7 fish. That can be B. neons or  cherry stain tetra  . Viviparous pygmy such as Heterandria formosa can be kept in a larger group. The keeping of killifishes  in a group of one male and three females is also interesting  .

In a beginner’s aquarium with a capacity of approx. 160 liters, the following can alternatively be kept, taking into account the requirements of the fish:

  • approx. 10 Black Mollys (females 10 cm, males 6 cm) approx. 16  guppies (females 6 cm, males 4 cm)
  • approx. 9 guppies and 2 catfish (14 cm)
  • approx. 16  red neon (5 cm)
  • approx. 12 red neons and 2  catfish
  • approx. 8 red neons and 6  armored catfish (6 cm)

4. How are baby fish fed?

Liquizell is a suitable food for young fish that are smaller than 2 mm.

Slightly larger juvenile fish can already eat so-called dust (dry) food, which is offered by various food manufacturers.

Finely ground flake food serves the same purpose.

In addition, young fish eat microorganisms in the aquarium that are invisible without a microscope and B. live on plants, roots and stones.

5. Do juveniles have to be placed in a spawning net or a spawning box?

As a rule, beginners are guppies or platys who get young animals first. The young of guppies are initially pale and colorless, platy babies are red like their parents from the beginning.

Since both species get numerous new young animals at regular intervals, it is sufficient to offer some hiding places in the aquarium. In addition to dense vegetation or the roots of floating plants, some loose filter floss can also be hung in the aquarium.

The wadding is tied to the cover or a floating, non-toxic object (table tennis ball, etc.) with a string. Since the juvenile fish collect in middle water layers and below the surface, their good flight instinct means they can quickly get to safety in the event of danger.

6. When can young fish be added to the other fish?

As soon as the young fish can no longer be eaten by the other fish, ie no longer fit in their mouth, young and old fish can be held together. For guppies and platies, this is roughly the size of the head of the largest fully grown guppy or platie.

7. Which fish species are good to start with?

First and foremost, fish for aquarists must be robust and tolerate small mistakes in keeping. In addition, beginners also have different tastes. Guppies and platies are popular and suitable as beginner fish. They are lively, have strong colors and tolerate most of the water quality that comes from the aqueduct in Central Europe. 

A small group of guppies or platies can be kept in an aquarium measuring 60 x 30 x 30 cm. It is sufficient if a couple of guppies and a couple of platys are used at the beginning, because they reproduce easily even in the beginner aquarium. Because they have live young, they are known as livebearers. 

In small aquariums there is even the risk of that there will soon be too many fish in the aquarium and the typical dangers of an overcrowded aquarium will arise. Especially if there are some hiding places for the young fish so that they are not eaten by their parents or other fish.

The risk of overstocking is avoided if the first fish e.g. zebrafish and harlequin barbels can be selected. These species do not place any demanding requirements on water quality either.

The colors of these species may not be as noticeable to beginners as they are for guppies and platies. On closer inspection, however, they turn out to be beautiful and interesting fish. The zebrafish in particular are always lively in the aquarium. For this reason, a 60 cm long aquarium represents the absolute lower limit in which 5 to 7 animals of one of these species are initially placed.

An aquarium with a length of 80 cm, in which more animals can be placed, is better. Since these two species shed eggs, reproduction is more difficult than with the life-bearing animals. In a normal beginner’s pool, a juvenile fish will rarely grow as the eggs and young are eaten very quickly. But first breeding experiences can be made with zebrafish if z. B. a pair can be placed in a small breeding aquarium to spawn.

After spawning, the parent animals are removed from the breeding aquarium.

The same applies to some of the more robust tetra species e.g. Sternflecksalmler.

An alternative to the usual recommendations for beginners is the steel-blue fish belonging to the killifish. While the males are beautifully colored, the females are quite inconspicuous.

A male with 2 – 3 females can be used in a well overgrown aquarium of 60 cm length with hiding places. If there is Java moss in the aquarium, there is a good chance that the carrots will multiply and that a young animal can hide from its conspecifics until it is too big to be eaten.

The rate of reproduction is therefore significantly lower than that of livebearers, but you can still enjoy young animals every now and then.

Please do not make fish soup

An aquarium should not have too many fish or too many different fish species together. Many species only feel at home in groups of around seven or more animals. Larger groups of one or a few fish species also look better than just one or two animals of many different species.

Consider the demands of the fish

The areas of origin of the aquarium fish have bodies of water with sometimes extremely different properties. The water from the African Lake Malawi is completely different from the water from the South American Amazon region. 

When selecting the fish, the requirements of the fish must be compared with the available water values. Fish kept in unsuitable water are prone to disease. Tetras such as Red neons tend to prefer soft water, while livebearers like guppies tend to prefer harder water.

8. Do damaged fins grow back?

It happens now and then that the fins of the fish are damaged. These can be small holes in the fins, but it can also go so far that the fins are completely frayed. The cause can be bite wounds in rank fights or diseases such as raft rot .

If only the soft parts of the fins are damaged, the damage usually heals quickly or the fins grow back if the conditions are good. If the hard fin rays are damaged or if the base of the fin is damaged, the fins may grow back crippled or not at all.

Human fingernails are comparable. If only the nail is damaged, it heals. Damage to the nail bed usually does not heal completely.

9. Why do fish swim at an angle in the dark?

At dusk or in the dark, the fish in the aquarium often swim a little tilted to the side or with the head down.

Since in nature the light always comes from above, the body alignment is simply based on the light.

This is how fish swim upright in nature. In an aquarium, light falls into the aquarium from the side at dusk or in the dark.

Since the fish orient themselves as usual based on the incident light, they align themselves in the direction of the light source and swim to the side or forward, depending on the incidence of light.

10. What should know about the different types of  fish in the aquarium?

You can use the time until fish can be put into your aquarium very well. Often go to various pet shops and take a look at the fish there. After a while you will see in which shop the fish are lively, where the fish hold their fins very close to their bodies because they are not feeling well, or where dead fish can often be seen. 

You will then also hear whether the seller is advising people and explaining everything well, or whether he only wants to sell as many fish as he can. Only buy your fish where the fish look healthy and the sellers are familiar with fish themselves.

There are so many fish that I can’t possibly describe them all. There are no good or bad fish either. All fish have their advantages and disadvantages. So that you can choose the right fish for you, I am now writing something about particularly popular fish.

Guppies, Platies and Black Mollies

These fish are beautifully colored and many people think they are beautiful. They often have young in the aquarium too. The young are easy to raise.

But the young also quickly become a nuisance. At some point there are so many juvenile fish in your aquarium that there is no more space. Because almost everyone already has these fish, you won’t find anyone to take the young ones away from you.

Not long ago a whole new type of guppy was discovered, the Endler guppies.

Neon fish

The neon fish are also beautifully colorful and popular. In order for you to feel really good, you need very soft water. Our water is almost always too hard for them. In such water they get sick easily and do not live as long as they could live.

If you have had an aquarium for a long time and are familiar with it, you can buy devices with which you can produce soft water yourself. That costs a lot of money. There are two types, both of which are called neons. Those with a red and white belly are really called neon tetra , those with a completely red belly are called red neon.

Mini sharks

Mini sharks are so popular because they look like tiny sharks. Who would have thought that. However, they become much too big for a normal aquarium. You need a pool when they get bigger.

Fire tails

They’re pretty too, with their black bodies and red fins. But they also get quite large and need a large aquarium. As they get older, they often quarrel with each other or with other fish.

Fighting fish

As the name suggests, they like to fight. You should never put two males in an aquarium. Otherwise they bite each other dead. The males also like to hunt the females. It can get so bad that the female dies of fear. Fighting fish come in many different colors and with different fin shapes.


Angelfish grow very large and need a huge aquarium. When they get bigger, they often quarrel among themselves. They may also eat small fish like the neon fish.

Algae eater

Under this name you can usually get catfish in the pet shop, which are actually called Otocinclus. They are therefore simply called Otto’s. The Otto’s are very sensitive when they are moved from one aquarium to another. Then they often die.


You’ve probably heard of the piranhas. While in reality they are not as dangerous as is always said, they are not good for an aquarium.

They have to be kept in swarms, take up a lot of space and are actually shy and fearful. You will then quickly feel attacked and can bite. If they are not feeling well, they can also bite each other. They need a lot of food like shrimp and other fish. Because they make a lot of dirt, you need a very large filter.

Piranhas can only be looked after by aquarists with a lot of experience and very large aquariums.

By now you already know a lot of things to look out for when buying fish. It’s pretty difficult to get the right fish, isn’t it? But do not worry, there are also fish that are suitable for beginners.

Armored catfish

There are many different types of catfish. Some stay small and have two black spots on their light body. That is why they are also called panda catfish.

All armored catfish like to look for food on the ground. Because they also like to dig in the ground with their snout, they particularly like sand as the bottom. You can then see how they take the sand in their mouths and let it out again through their gills.

Armored catfish are peaceful and like to live together in small groups. You should have at least 5 armored catfish together in the aquarium so that they are really lively. Many species grow to be about 5 or 6 cm long.

Harlequin harlequin

The harlequin harlequin like to swim around together in the middle of the aquarium. Sometimes everyone swims together in a small school, sometimes everyone swims around on their own. When they are comfortable, they look very good with their black spot on the reddish body. You should also have 5 or more of the harlequin harlequin if possible. Harlequin harlequin grow to be about 4 cm long.


The zebrafish have beautiful dark blue horizontal stripes.

They swim wildly through the aquarium all day. In doing so, they often hunt back and forth very closely together just below the surface. Often times it looks like they’re playing catch. There is also a species that has no stripes but small dots and is therefore called leopard harlequin.

You shouldn’t care for less than 5 zebrafish or leopard rasbora, then they will get bored. Zebrafish can grow to be 2 inches long.

11. Which type of fish is the best recommendation for my aquarium?

Armored catfish, wedge-spotted barbels and zebrafish are nice, pretty fish. They get along with each other and with other fish species. You are cheerful and do not get sick easily. If I were you, I would put these fish in the aquarium.

How many fish of each species you can put in the aquarium naturally depends on how big your aquarium is. The fish pee and shit too. The more fish and the bigger the fish, the more dirt they make. Too much dirt makes the fish sick and die. For every centimeter (cm) that the fish grows long, you need one liter, or even better two liters, of water.

An example:

You have 5 young fish. When the fish are fully grown, 3 fish are 5 cm and 2 fish are 10 cm long. So you calculate: 3 * 5 cm = 15 cm and 2 * 10 cm = 20 cm. Together it makes 35 cm. Your aquarium must therefore have at least 35 liters of water, or even better 70 liters. Of course, more water doesn’t do any harm.

12. How do I introduce new fish into my aquarium?

When your aquarium has worked for six weeks without fish, you can insert the first fish. First of all, buy only one species of fish. The zoo dealer packs the fish in a bag with water from his aquarium.

When you get home, you simply put the bag in your aquarium. It is best to turn off the lights so that the fish are not so scared of the new aquarium. After an hour, the temperature in the bag and in the aquarium will be roughly the same. Now you can open the bag. But be careful that the new fish cannot swim out. 

Now use a clean glass to fill the bag with some water from the aquarium. Use no more than a quarter of the water that fits in a normal drinking glass. The fish must first be accustomed to the water in your aquarium. This has to happen as carefully and slowly as possible. Wait a quarter of an hour and fill the bag with as much water as you did before from the aquarium. 

It continues like this until you have twice as much water in the bag as at the beginning. Always alternate between waiting and filling. It takes a while, but you have had six weeks of patience, and now you still have that patience.

When you have doubled the water in the bag, carefully pour the water with the fish into a bowl or bucket. Be careful not to leave any fish in the bag without water. Now you catch the fish carefully and individually with the fishing net and bring them into your aquarium. At first the fish are frightened and pale. But after a few hours they should swim around happily.

There are recommendations that make it quicker to get used to and that are sometimes printed on the bags for the fish. But there are also recommendations to get the fish used to the new aquarium even more slowly. The method described here has proven itself for many fish species and helps the fish to slowly get used to the new environment without experiencing too much stress.

Now you have enough to do to consider which fish you want and how many of them fit in your tank. If you have an aquarium that is 60 cm long, 30 cm deep and 30 cm high, then about 50 liters of water will fit in. Let’s put fish in it, for example:

5 armored catfish: 5 * 5 cm = 25 cm and

5 zebrafish: 5 * 5 cm = 25 cm

So the aquarium is already full with the 10 fish. Do not put more in your aquarium. You only get sicknesses and unhappy fish. Too many fish make the water dirty, get sick and eventually die.

Beginner questions: CO2 fertilization in the aquarium


Plants absorb CO 2 along with other nutrients during the day. In order for plants to thrive optimally, all the necessary nutrients must be available in sufficient quantities. If there is too little CO 2 in an aquarium , fertilization with CO 2 is worthwhile.

However, the other nutrients must also be present in sufficient quantities. The CO 2 content in the aquarium can be measured with water tests. If the test finds too little CO 2, fertilization should be carried out with CO 2.

13. How does CO2 fertilization work?

So-called yeast fermentation is an inexpensive way of fertilizing with CO2. To do this, you fill e.g. a 5 liter canister with 4 to 4.5 liters of water. Dissolve 1 kilogram of sugar in it and add 1.75 to 3.5 grams of dry yeast. 1.75 grams is a quarter and 3.5 grams is half of a 7 gram bag of dry yeast for baking.

Everything is mixed well. Since the amount of yeast determines the strength of the CO 2 production, the exact amount must be optimized with increasing experience. Gelatin uses a more refined method of yeast fermentation in order to achieve a more uniform CO 2 production.

A small hole is drilled into the screw cap of the canister into which an air hose with a diameter of 4/6 mm or a connection for the air hose is pressed. The connection is well sealed, e.g. with a hot glue gun. An air hose leads from the canister into a small washing bottle with about half a liter content, which is about half filled with water. The tube ends about an inch above the bottom of the bottle.

A second air hose leads from the wash bottle to the aquarium. For this purpose, two openings for the air hoses are drilled in the lid of the washing bottle and sealed again. The second hose between the wash bottle and the aquarium does not protrude into the water of the wash bottle, but only into the upper air or gas-filled half.

Some manufacturers of aquarium accessories offer ready-made CO 2 systems based on this principle. These are usually offered with names such as bio-CO 2 etc. Dried yeast is hidden behind the mysterious microorganisms. Since these systems can be refilled with self-made mixtures, they are a good alternative for aquarists who do not want to tinker the system themselves.

The disadvantage of yeast fermentation is the poor control of the amount of CO 2 generated.

In addition to some other methods, there is the option of introducing CO 2 into the aquarium using a CO 2 system with a pressurized gas cylinder. The compressed gas cylinder should not be dimensioned too small; otherwise it has to be refilled constantly. Instead of a 350 gram bottle, a 1.5 kg bottle is usually the better alternative. Often only the price difference for the bottle has to be paid additionally.

Beginner Questions: Problems in the aquarium

Aquarium pH, GH, and KH for BEGINNERS​

14. Why do I have Algae in the new aquarium?

beginner questions

Algae cope better with unfavorable conditions in the aquarium than aquarium plants. When the conditions for plants are or become unfavorable, algae spread quickly. So that the plants can successfully compete with the algae and ultimately push the algae back, they need good growth conditions.

The rule here is that all the necessary nutrients must be available in sufficient quantities. If only one nutrient is insufficiently available, the plant cannot thrive optimally, even if the other nutrients are in excess. The excess then benefits the algae.

If the plants do not thrive despite regular addition of plant fertilizer, possible causes are a lack of CO 2  or unfavorable lighting conditions. The substrate should be 7 to 10 cm high and not too coarse.

Since different types of plants also have different demands on light, fertilization and the amount of CO2, the right choice and composition of plants also plays a significant role. On the leaves of slow-growing plants, such as the small spear leaf (Anubias nana), algae will form on the leaves over time if the plant is illuminated too strongly. In an aquarium with strong lighting , shading by other plants must be ensured.

Plants like the Indian water star (Hygrophilia difformis) have a high need for nutrients and need strong light. If these plants are heavily fertilized in an aquarium with a lack of CO 2 , the excess fertilizer can lead to a strong increase in algae. A balanced ratio of nutrients must be guaranteed by adding CO2.

You can get rid of excess nutrients by changing the water. Therefore, frequent and vigorous water changes can be a successful remedy for algae. Extremely fast-growing plants also consume excess nutrients. Hornwort (Ceratophyllum demersum) can grow 10 to 30 cm in a week if sufficient nutrients are available in a balanced ratio. Short-term water changes are suitable, medium- and long-term fast-growing plants to eliminate nutrient surpluses.

15. What are the most common causes of fish mortality in beginner aquariums? And how do I prevent it?

The most common cause of the rapid and massive death of fish in newly set up aquariums is probably too short a running-in period. But other causes can also be considered.

Possible causes of fish death

  • The running-in time of the aquarium was too short (nitrite value too high).
  • The fish were moved too quickly.
  • Toxins were in the aquarium (copper from the water pipes, cleaning agents, cleaning sponges, etc.).
  • Too much feeding when the aquarium is not run in.

The cleaning of the aquarium is easily overlooked as the cause of fish deaths, e.g. removing algae from the panes. New cleaning sponges may contain production residue or detergent. Therefore, only artificial sponges that have been thoroughly rinsed with clear, possibly boiling water may be used to clean the aquarium panes.

Linen cloths filter floss and filter sponges are also suitable. Before working in the aquarium, hands should also only be washed with clear water, never with soap. Watches, rings, bracelets and other items that could bring contaminants or toxins into the aquarium must be removed.

If many fish die quickly at the same time, there is always a suspicion of poisoning. Therefore, frequent and vigorous water changes are recommended as a quick and immediate measure.

If nitrite poisoning is suspected, around 75% of the water should be changed at least twice a day for a week. During this time, sludge is not extracted and the filter is not cleaned. The amount of feed is reduced by half. New fish should be bought after 14 days at the earliest.

It is safer to check the nitrite level daily and to change the water as often as necessary until no more nitrite can be detected. Only when no nitrite was detectable for 14 days can new fish be introduced gradually.

Even with the strongest growth of algae, no chemical agents should be used to destroy algae. As a rule, they damage the plants more than the algae and seriously disturb the balance in the aquarium. Some of these agents also include copper, which is useful for invertebrates, e.g. shrimp and snails, is fatal.

16. Why does my aquarium smell so bad?

A newly set up and not yet fully run in aquarium can smell a bit unpleasant at the beginning. This indicates a high biological load on the water. Bacteria that break down pollutants must first settle in high enough numbers. The water pollution is reduced by changing the water. If the aquarium has a biological filter and if the aquarium is not too crowded, the smell will decrease after a few weeks.

Stronger stench indicates putrefactive processes, the causes of which must be determined and eliminated.

17. What common problems are expected in new aquariums?

Once problems have arisen in an aquarium, it often takes a while until the aquarium is stabilized and can be operated without problems. The starting point for initial problems is usually excessively high nitrite levels. The cause is usually too short a running-in period or too much feeding of the fish after the running-in period.

Most species of fish eat constantly and do not feel full. Beginners can easily conclude from this that the fish are hungry and are giving way too much food. The biological transformation processes in the aquarium ultimately create nitrite. Newly established aquariums are often not yet populated with bacteria that break down nitrite so that the nitrite that arises from the food is broken down quickly enough.

For this reason, a newly set up aquarium should be fed particularly sparingly. Feeding can be dispensed with once a week. If you then slowly increase the feeding to the normal value, which, however, also has to be economical, there are usually no noticeable nitrite values.

If the fish show signs of nitrite poisoning, the nitrite content of the water must be reduced immediately by numerous water changes until no more nitrite can be detected. However, these water changes delay the colonization with bacteria that break down pollutants, so that it takes longer for the aquarium to reach a state of equilibrium.

At the same time, the many water changes cause stress in the fish and act as a burden. This delay must be accepted because the impending poisoning must be averted. However, the development can be observed and controlled with a good nitrite test.

In such cases, the feeding can be drastically reduced or stopped completely for a few days. This gives the bacteria the opportunity to multiply and to adapt their degradation capacity to the amount of pollutants. The aquarium climate usually stabilizes very quickly.

Beginner Questions: Aquarium Size


18. What size should a beginner aquarium be?

  • if you don’t like the hobby, the expenses weren’t so high.
  • even small aquariums can be operated without any problems.
  • In small aquariums, errors and problems are recognized immediately.
  • Sources of error are more easily identified than in large aquariums.
  • Countermeasures for problems such as B. water changes can be carried out faster in small aquariums than in large aquariums.
  • in small aquariums the effect of measures taken is immediately recognized.
  • In small aquariums the diverse interrelationships in the aquarium are recognized.
  • if you can create a stable equilibrium in a small aquarium, you can also create it in large aquariums.
  • Regular maintenance measures such as water changes, plant care etc. are carried out faster than in large aquariums.

19. Why should my first aquarium be big?

  • large aquariums are less work than small aquariums.
  • large aquariums are more fun than small aquariums.
  • Errors and changes have a slower effect than in small aquariums.
  • Errors and changes are not as serious in large aquariums as they are in small aquariums.
  • Changes are sometimes not even noticeable because they are eliminated before they have an impact.
  • Diseases caused by overstocking or other stress break out later than in small aquariums.
  • it takes longer for too much sludge to cover the floor.
  • Countermeasures can be taken before problems become critical.
  • Beginners often want many different fish that only have enough space in a large aquarium.
  • More fish can be kept in larger aquariums. Either more fish of a few species or more different fish species.
  • it takes longer for a large aquarium to become overcrowded.
  • large aquariums are more stable than small aquariums.
  • Regular care measures such as plant care must be carried out more frequently than in small aquariums.

20. Why is the size of my first aquarium unimportant?

  • the size should be selected according to the financial and spatial conditions.
  • small and large aquariums are fun.
  • There is a risk of overstocking in both small and large aquariums.
  • In both small and large aquariums there is a risk of fish species that do not match each other being used.
  • Beginners do not recognize problems in either small or large aquariums before they become critical.
  • Overall, the maintenance effort for small and large aquariums is the same.
  • In both small and large aquariums, beginners tend to overfeed.
  • In both small and large aquariums, beginners will inevitably make mistakes.
  • There will be deaths due to lack of experience in both small and large aquariums.
  • Because of the higher costs, difficulties with large aquariums are more frustrating than with small aquariums.

21. What is the best advice for a beginner regarding tank size?

A general recommendation for a small or large aquarium to start with does not make sense. Every beginner has to weight the listed arguments for himself and decide accordingly. Of course, the size of the aquarium also depends on the space available. The aquarium depth should always be as great as possible, as this will result in better design options.

Another consideration is the desired lighting. For aquariums with a length of 120 cm one rarely finds inexpensive tubes e.g. in the hardware store. For some aquarium sizes, tubes of a shorter length and thus a lower wattage must be used than would actually be necessary for the luminance. The aquarium is then relatively dark. However, this can be at least partially offset by suitable reflectors or the selection of suitable plants.

It is more important than the question of the aquarium size to get an overview of as many aspects of the aquarium as possible before making a purchase decision and to seek advice from experienced aquarists as early as possible during the entire initial phase.

Beginner Questions: Cleaning the aquarium sand

How to Clean Your Aquarium Sand… the Easy Way!

22. How do I wash out aquarium sand?

If necessary, new aquarium sand can simply be washed out. Some simple methods have proven to be suitable for this, which differ in detail, but all are based on the principle of simply flushing the sand through with water.

A bucket or other vessel is partially, e.g. to a third, filled with sand, then as hot water as possible is turned on fully. You can use a shower or a hose. The end of the hose is used to stir the sand down to the bottom. When the bucket is full, the water with the suspended dirt particles is poured off. The process is repeated until the water is clean.

Different variations:

  • Fill the sand in portions into a bucket and rinse through.
  • Pour sand into an enameled cooking pot and rinse with a full, hard shower jet.
  • Fill sand into nylon stockings and rinse.

Opinion 1: Not all sand has to be washed.

Some sands contain loam or clay. Such sands can often not be washed so thoroughly that the aquarium will not become cloudy later. If the first, lowest soil layer on these sands is only roughly washed out, you have a long-term fertilizer or a good store for fertilizer at the same time.

Pre-washed or not heavily polluted sand does not need to be washed at all. If necessary, fine particles and sand dust can be sucked up with a sludge bell the first time the water is changed, so that they are not repeatedly stirred up and cloud the water.

Usually sand treated in this way does not clog, even if there are fine particles in the substrate.

Opinion 2: Quartz sand should always be washed.

The washing out of quartz sand primarily serves to separate the grain size. This ensures that no smaller particles clog the pore system of the sandy soil and that diffusion functions properly.

These finer particles will not collect on the surface of the sand in order to be sucked off, but will be built into the pore system in larger spaces. It is even less of a long-term fertilizer, since even fine sand particles do not release any usable nutrients, but merely prevent or hinder the diffusion of nutrients into deeper sand layers.

Quartz sand should therefore always be washed out with a sharp water jet in order to achieve the most homogeneous grain size possible. Cold water can be used for this. In this context, warm water does not have any advantages, only the risk of higher pollution (e.g. copper).

23. Should I use hot or cold water to wash aquarium sand?

A possible pollution of warm water by copper is only to be feared with warm water boilers or copper pipes. With copper pipes, to be on the safe side, you can let the water run off for a few minutes before washing starts. Hot water from boilers should not be used.

Fresh and clean sand is not always used. Some dirt particles dissolve better with hot water. Hot water can possibly kill some organic components such as algae spores or fungal spores that may be contained in the sand.

Beginner Questions: Aquariums suitable for children

24. From what age are aquariums suitable for children?

The age from which children can own aquariums cannot be stated in general terms.

To consider is:

  • Can and will the child take responsibility?
  • Does the child only want an aquarium because acquaintances also have an aquarium?
  • How long has the child shown interest in other things (toys, etc.)?

An aquarium should only be purchased if the parents are willing to help the child care for it. The more the parents are willing to help the child with the care of the aquarium, the earlier an aquarium can be purchased. Basically, an aquarium for children should be operated with the simplest possible means.

A complete set usually contains the necessary technology such as an aquarium, cover, lighting , heatingand filters. Only two or three species of fish should be cared for that can be kept in the tap water available, are not difficult to care for and are not shy.

Livebearers are interesting for children because of their colors and how often they have young. The plants should be robust. The substrate should consist of fine gravel or sand so that no organic substances can penetrate and rot.

The necessary care must be explained in a child-friendly manner. It is difficult for children to understand that water changes are necessary because the nitrite content would otherwise lead to illnesses or fish death.

It is immediately understandable that even fish do not want to swim in their own dirty bath water. Regular maintenance of the aquarium can be made familiar to children by having parents and children mark the days for the water change on the calendar or create a calendar that the children paint with symbols for the respective activity. The possible death of a fish is also unproblematic for children if the explanation is correct.

Smaller children between the ages of 2 and 3 are fascinated by aquariums and especially by baby fish. They also like to hold the hose when changing the water. However, there is a risk that children of this age will throw toys or other objects into or against the aquarium.

It must also be expected that they will reach into the aquarium to stroke the fish, or that they will want to save the fish from starvation by feeding a whole can of flake food. Despite all the explanations, an aquarium in a room where small children are unsupervised is therefore a risk.

Under supervision and control, children can carry out daily tasks from kindergarten age, such as feeding, checking the temperature, checking whether the filter is running, etc.

At around 6 years of age, children are interested in the different types of fish, what they are called, what they eat, why some fish swim up or down in the aquarium, etc. At this age, children can also help with care. However, there can also be a lack of desire to help.

First and foremost, children of this age should be instructed to watch the fish and to alert their parents if anything is abnormal. Nevertheless, the parents have to watch the fish themselves. The children should only feed the fish under supervision. Under supervision, they can also help with water changes , water tests, etc. Shaking the tests and watching the color change is fun and interesting.

From around the age of 8, children can maintain their aquarium independently, ie carry out feeding, water changes, etc. after the parents have explained what to do and at what intervals.

Often the initial zeal wanes after a while and the necessary activities are no longer carried out or only insufficiently. For example, water is no longer changed, only evaporated water is refilled. Diseases and deaths among fish are the result.

From about 10 to 12 years of age, children are able to take care of an aquarium on their own. Nevertheless, even at this age, the parents must monitor whether they are still interested in the aquarium or whether the aquarium is being neglected due to other interests.

Beginner Questions: Cleaning the floor of the aquarium

The substrate plays an important role in the biological degradation processes in the aquarium. The sludge itself can also contribute to a stable aquarium climate due to its buffering effect. Disturbing the substrate and removing sludge can therefore lead to an unstable overall system.

In a well-run-in and not too crowded aquarium, the bottom does not have to be cleaned at all. In an aquarium with a volume of 240 liters and gravel as the substrate, there was not a handful of sludge in the ground after 12 years, although sludge was never vacuumed.

If too much sludge accumulates on the floor or in the floor, cleaning is useful. It is better to vacuum more often and only a part than rarely and a lot, so as not to impair the aquarium climate too much. A rare but thorough cleaning can lead to increased algae growth and even to the outbreak of diseases such as Ichthyo .

Experience also shows that too frequent cleaning of the soil affects the growth of the plants. The disturbance of the roots and the lack of sludge as a producer of nutrients probably play a role here.

The exact cleaning intervals depend, among other things, on the density of the stocking, the feeding and the vegetation. The more manure, fodder and plant residues there are, the more often it has to be cleaned.

An important aspect here is the prevention of rot. If foci of putrefaction have already formed in the soil, the cleaning process releases toxic gases that endanger the fish population. As an initial rule, about a quarter of the sludge can be sucked off with every second water change. Based on this, the frequency and the amount sucked off are changed depending on the mulma attack.

There are aquariums in which the bottom is cleaned weekly, but also aquariums in which the bottom is not cleaned for many years. In between there is probably every possible variant. It is important that the entire aquarium system is as stable as possible.

25. Is it necessary to clean the floor of the aquarium regularly?

There is no general answer to this question. Aquariums are too diverse for that. However, there are some indications when floor cleaning makes sense and when it is not.

26. What pollutes the floor of the aquarium?

Over time, food residues, dead plant parts and fish droppings collect on the aquarium floor, especially in the form of sludge. Depending on the type of soil, these organic substances accumulate on the soil surface or penetrate deep into the soil.

In sand with a grain size of less than 1 mm, almost all particles of these substances remain on the surface; the coarser the grain, the more and deeper the particles penetrate. A lot of material can penetrate into gravel in particular by trickling through the cavities.

Organic material can also penetrate the soil through the setting of plants or fish digging in the ground. If there is insufficient oxygen supply, putrefaction processes can occur in the soil. Foci of putrefaction can be recognized by black spots in the ground, by gas bubbles rising from the ground and above all by the unpleasant smell of rotten eggs.

27. Can the substrate act as a filter?

Like a filter, the substrate offers the bacteria that break down harmful substances a suitable surface for colonization. In comparison to the filter, the settlement area in the soil is extremely large. As a rule, the water only flows slowly through the soil, so that the soil also acts as a biological filter.

In comparison, the flow rate of conventional pot filters is so high that many of these filters carry out almost purely mechanical filtering and only have a low biological filter performance. I.e. that, like a sieve, only coarse dirt particles are caught by the filter, but the pollutants dissolved in the water are only broken down to a small extent.

Also in these quick filtersAs pollution increases, zones form in which the water flows more slowly. On the other hand, zones often form through which the water flows so quickly that it is not biologically filtered at all in these zones.

The ideal case

In the ideal case, three layers form in the ground, which theoretically even take over the entire filter work, if the aquarium is completely set up according to ecological aspects. The height of the floor must be at least 7 to 10 cm.

Nitrification takes place in the top layer and de-nitrification in the middle layer. In the bottom layer, the soil is enriched with minerals that are created by bacteria when they breathe sulfate. These minerals serve as nutrients for the plants. The same types of bacteria live in all layers. The number of bacteria of the different species depends on the amounts of oxygen and nutrients present in the respective layer. Nutrients are the metabolic products (fish droppings, plant residues, sludge, etc.) that penetrate the soil. The productivity of the layers thus adapts to the nutrient situation.

In such an aquarium, only a foam filter is necessary to remove coarse dirt particles.

Without a substrate and without a filter, nitrification would take place in the aquarium water. Bacteria floating freely in the water would find enough nutrients to multiply strongly in the water.

This would make the water cloudy. In principle, a filter ensures that so many bacteria settle in one place in the aquarium that there are not enough nutrients in the free water for other bacteria, thus preventing the water from becoming cloudy.

The reality

Since most aquariums are not set up according to ecological criteria, both an additional filter for nitrification and regular water changes to remove pollutants are necessary.

In order to achieve an approximately equilibrium, only one finger-length fish should be kept for every hundred liters of water. In addition, it cannot be guaranteed that water flows through the substrate in such a way that all metabolic products are completely converted.

For this reason, the substrate represents an additional filter in the aquarium, the effect of which should not be overestimated or underestimated.

Beginner Questions: The first aquarium

28. What is everything I need for my first aquarium?

  • A glass case, the aquarium
  • A base on which the aquarium stands
  • A back wall
  • Gravel
  • A heater
  • A filter
  • A cover with lighting
  • A thermometer
  • Aquatic plants
  • A hose
  • A fishing net

The pet shop may want to sell you more things. But you don’t need more to start with.

29. What should I watch out for when buying my first aquarium?

In the pet shop you can buy all the parts listed above individually. There are also complete sets in which many parts are already included and where the things also fit together. The sets also usually cost less money than all of the parts individually. You then buy the missing parts.

Make sure that the things are from good and well-known companies. Good companies are, for example, Eheim, Tetra, Jäger, JBL and Juwel. Good complete sets are available from MP. Often the name of MP is only small on the box and the name of the pet shop is big.

Look carefully and ask the zoo dealer. In MP boxes there is usually always an Eheim filter, a heater from Jäger, lighting from MP itself and other parts. The sets from MP are available in many pet shops, hardware stores and garden centers. If a store doesn’t have one, just check the nearest store.

30. How do I set up my first aquarium?

Before you set up your aquarium, first read through all the aquarium instructions, heater instructions, and filter instructions. Although boring, it is important to read and understand everything. If you don’t understand something, ask your parents. When you have understood everything, you can start building.

If the aquarium is not on a completely smooth surface, it can break apart. Some aquariums have a frame at the bottom. You then also have to put the aquarium in the frame. The frame ensures that nothing happens. If there is no frame, then you have to place the aquarium on a mat. Correct aquarium documents are expensive.

These finished aquarium pads are mostly black foam rubber mats that have already been cut for the corresponding aquarium size. But you can also buy a styrofoam sheet at a hardware store for little money. You cut it with a sharp knife so that the aquarium stands firmly and securely on it. Take care of your fingers as you cut, or let someone else help you with this.

You can use a back wall printed with pictures of plants as the back wall. Black, green, or blue cardboard also looks great and is cheap. You can also draw plants on cardboard yourself. What you like is allowed. But remember that the back wall is difficult to change later.

Happy pink cows on a blue and red checkered background don’t really matter to the fish, but in the long run it might not be that nice. Cut out the back wall to fit and simply stick it to the rear pane with scotch tape. Use a lot of scotch tape so the back wall doesn’t curl later. That looks bad and once there is water in the aquarium, it is difficult to change that.

31. How do I soil in the aquarium?

So that the fish do not slide around on glass and so that you can put plants in the aquarium, you fill the aquarium with sand or gravel, whereby you can best fix the plants in gravel 3 – 5 mm grain size. The floor must be at least 2 inches high. You can calculate how much you need roughly.

Length of the aquarium times the depth of the aquarium times the height of the bottom times 1.6. Divide the result by 1000.

An example:

Your aquarium is 60 centimeters long and 30 centimeters deep. The floor should be 5 centimeters high:

60 x 30 x 5 x 1.6 / 1000 = 14.4

32. What steps do I need to take when setting up my first aquarium?

Properly set up the substrate

So you need about 14 kilos of gravel or sand. Often there are 12.5 kilos in a sack. That is enough then.

If you use sand, make sure that there is no clay in it; otherwise your water will be very cloudy at first. You can also use sand for sandboxes. But buy new sand. Sand that dogs and cats have put in is not suitable for the aquarium. There must also be no remedy for fungi or other things in the sand.

With gravel, the grains must not be too big; at most 2 millimeters. Otherwise food leftovers will fall in, which can spoil and poison the water. The gravel must also not have any sharp edges. Otherwise the fish may get injured.

You can buy the substrate cheaper at a hardware store than at a pet store. But make sure that the substrate has not been chemically treated. Otherwise the fish could get sick or die.

First you have to wash the substrate. Pour the sand or gravel into a bucket or tub. Fill the container with warm water and simply stir the sand or gravel with your hand. Pour off the dirty water. You keep doing this until the water stays reasonably clean even when you stir it. It doesn’t get completely clean.

It is best to wash the substrate outside so that the water does not clog the drain if you accidentally dump some sand or gravel. After washing, carefully pour the substrate into the aquarium and distribute it on the floor.

Properly clean the aquarium and all equipment

When the substrate is in the aquarium, you next clean the filter, heater and thermometer. They have thick suction cups that have to be pressed firmly against the panes. Sometimes the teats go off again by themselves. Then you just have to press it down again. Sometimes the teats come off with difficulty.

So think carefully beforehand where you want to fix it, preferably in a corner at the back of the aquarium. The cables must reach the socket. If possible, use a multiple socket or distribution socket, because many devices for the aquarium need electricity and therefore have a plug.

Add in decorations

If you want to add stones or roots to the aquarium to make it look more beautiful, you should do it now. You can then try what it looks best without wetting everything. Many roots float on the water first. You will need to let them sit in a bucket of water for a few days, until they are soaked and submerged. Or you can buy a root straight away that is heavy enough and does not float.

Before you put roots and stones in the aquarium, wash them down in the shower or bathtub with hot water to clean them.

Let water into the aquarium

When the soil, equipment, stones and roots are in the aquarium, you let water in. But put some towels down, you will have to dry yourself off a few times. The water must be about as warm as it will be later in the aquarium.

When it’s a little cooler, you can easily see whether the heating is OK. Place a small plate on the floor and let the water run on it. Then the whole ground doesn’t spin around. The bucket from which you let the water into the aquarium must be higher than the aquarium. You put one end of a hose into the water in the bucket.

You hold the other end over the aquarium. Then you suck briefly and firmly at the end of the hose above the aquarium and then quickly hold this end over the plate. When sucking in, your head must be lower than the surface of the water in the bucket.

You have to practice this a few times before it works. If you suck too short or not hard enough, the water won’t come through the hose. If you suckle too hard or too long, the water will come out so quickly that water will come into your mouth. Then just gulp it down, it’s just water. Yes, you need both hands and your head at the same time, but with a little practice it will work. Just practice in the shower or bath beforehand.

First only fill in about 8 to 12 inches of water. Then you can insert the plants without getting completely wet and at the same time see roughly what it looks like with the plants. If you don’t like something, you can easily rearrange it.

Plant aquarium

The plants are mostly in small pots with lots of plastic holes. Sometimes the roots have grown through the holes and you can’t just pull the plants out of the pot. Then just cut through the pot with scissors until the plants and roots are out of the pot.

Almost always several plants grow in one pot and the roots are in some strange brown stuff called Rockwool. Carefully wash off this rock wool in a small bowl of water and carefully separate the individual plants. You carefully cut off yellow leaves.

You can cut the roots a little shorter with sharp scissors; they will then continue to grow faster. Use your finger to drill small holes in the bottom of the aquarium and carefully insert the plants. Then you carefully push the substrate against the plant with your hand until it is stuck. There are plants that have very long stems or stems and are therefore also called stem plants.

If you like everything, you fill the aquarium completely with water. But don’t fill it up to the brim, leave 5 centimeters free at the top. Some aquariums also have a marker that shows how high the water may be.

Put the aquarium into operation

Next, you now set the heating. Most heaters have two markings at the top. The water must be higher than the lower mark and lower than the upper mark. At the top of many heaters is a small wheel with a small arrow. There are numbers next to it.

  • Turn the wheel so that the arrow points to the temperature you want the water to be.
  • If your heater looks a little different, you have to read the instructions for how to set it correctly. When the heating is set, you plug the heating plug into the socket.
  • If the set temperature is higher than the temperature of the water, a small lamp lights up.

Whenever the lamp lights up, the heating is on. If the water is warmer than the temperature on the heater, the lamp stays off.

The water slowly gets colder and as soon as it gets too cold, the heating starts. However, the displays of the thermometer and heater are not always exactly the same. It is also okay if, for example, you set the heater to 27 degrees and the heater comes on when the thermometer shows 25 degrees. Refer to the temperature shown on the thermometer.

33. What else should I add into the aquarium after I have added the water?

The pet shop will probably recommend water conditioners and fertilizers.

Water purifier is mostly a blue looking liquid. You can put this in the aquarium, but you don’t have to. You should only use a water conditioner if the aquarium water really smells like a swimming pool. Then there is chlorine in the water and that is harmful to fish. How much water conditioner you need is written on the bottle or on the package.

You should add some fertilizer to the water so that the plants grow well. But first of all only take half of the amount that is written on the bottle or package. Otherwise a lot of algae will grow quickly in your aquarium. Algae come naturally in every aquarium anyway.

As long as there aren’t that many, it doesn’t matter. But when there are a lot, it looks ugly. Then they can even take away all fertilizer or light from the plants until the plants die. If you have only a few algae later and the plants are growing poorly, you can use more fertilizer.

34. What should I not forget for the maintence of the aquarium?

As soon as your aquarium is set up and you have added fish, you have to observe your fish and your aquarium daily. Check the temperature and see if the filter is still pumping water. Pay particular attention to how the fish behave. If they behave abnormally, such as keeping their fins close to their bodies or all gasping for air, they may be sick.

How to feed

Feed your fish once or twice a day. Only give them as much food as they can eat in two minutes. Don’t be fooled, they are always hungry and eat until they burst. You can also stop feeding once a week. Too much feed makes them sick in the long run. The fish don’t starve to death as quickly as many people think.

Snails in the tank

With the plants, snails can also be added into the aquarium. A couple of snails come in handy. But if your aquarium is teeming with snails, you are feeding way too much. If you feed less, there will be fewer snails again.

Racing snail

The racing snails may be named because they look like painted racing cars. In any case, you don’t need to be afraid that they will run away from you; although they should be pretty quick in the dark. Maybe that’s why they are called racing snails. Racing snails do not come into the aquarium by chance with plants, they have to be bought.

However, they can sometimes occur at night through gaps in the aquarium cover, e.g. for technical cables, crawl out and die.

Because racing snails are almost always caught in the wild, they should be kept by experienced aquarists. Many racing snails only eat algae and not ready-made food. They starve to death if they are not specifically supplied with cultivated algae.

35. How do I take care of my aquarium?

Your aquarium needs to be looked after once a week. Always do this on the same day, then you won’t forget it either. You have already read a few times that the fish also make the aquarium water dirty. The filter removes some of this dirt, but not all of it.

Unfortunately, you can’t tell from the water how much dirt is in it. Therefore, as a precaution, you have to replace a quarter of the water in the aquarium with fresh water every week.

But before you start taking care of it, be sure to pull all plugs out of the socket. Otherwise, if you reach into the water, you could be electrocuted and die.

You get the old water out of the aquarium with a hose, just like when filling it. When pulling out the water, the bucket must be lower than the aquarium. And of course you have to suck at the end of the hose at the bucket. Be careful not to get any fish too close to the tube. If he is sucked in, he can injure himself.

Next you look at the plants. You cut off leaves that are no longer nice and green with sharp scissors or snap them through with a fingernail. You take stem plants that have grown too big out of the ground and carefully cut them in half. You can even replant both parts. Just don’t get them too close, otherwise the lower leaves won’t get enough light and will fall off.

A 3 meter stalk with 2 leaves at the top just looks ugly. If there is not enough space left in the aquarium, only plant the part that is most beautiful. Just try it out. If you have replanted a few times, you will already notice how far apart the plants have to be to keep them beautiful.

If you have noticed during daily observation of the aquarium that hardly any water is coming through the filter, you have to clean it now. Many filters have foam inside. You squeeze it out a few times in the bucket with the old aquarium water and put it back in the filter. You have to read the instructions for exactly what you have to do with your filter.

If there are a lot of algae on the panes, you can now carefully rub them off with a sponge. Be careful not to get into the ground and scratch the windows with sand or gravel. Algae on plants can be gently rubbed with your fingers, but all algae will not come off.

Finally, the water is topped up again. The new water must have the same temperature as the aquarium water. You already know how to fill in water. You should definitely put some fertilizer in the new water. But at most as much as the new amount of water needs. When you are finished and no longer have to reach into the aquarium, you can put the plugs back in the socket.

Beginner Questions: The 5 largest aquarium fish

Today there are aquariums in a wide variety of shapes and sizes. However, if you want to buy an aquarium, you should consider in advance which inhabitants you want to expose in it. Because while many ornamental fish only reach a size of two to three centimeters, there are certainly aquatic animals with a body length of ten or more centimeters. Of course, these also need a correspondingly large living space.

36. Which are the largest Aquarium fish?

The South American catfish

The south American catfish habitats brackish water, i.e. water with a salt content of up to one percent, at river mouths, while the young fish, which can reach a body length of up to three centimeters, live in fresh water. This fish is called mini shark because its appearance is reminiscent of a shark.

The South American catfish has its natural habitat on the Pacific coast between southern California and Peru. The West American catfish feeds primarily on crabs and smaller fish, but occasionally also eats green fodder. As long as the catfish is not fully grown, it lives and hunts in groups. In adulthood, the animal can reach a body length of up to 45 centimeters

The Pennant Carp

Pennant carp is a sucking carp whose original home is in India. While the bodies of young animals are brownish in color with black stripes, adult males have a distinct red color that darkens with age. Typical of this fish are its triangular and high dorsal fin and the fleshy, thick lips. Pennant carp reach an average body length of 40 to 60 centimeters.

Pennant carp need clean water because they are sensitive to when the nitrate content is too high. The fish feel most comfortable when the water has a pH value between 6 and 7 and a temperature of 24 degrees; but they can also survive if the water – for example in the garden pond – has a temperature around freezing point at times.

In addition to algae, small aquatic creatures and crustaceans are also the preferred food of pennant carp. These fish, which can live up to 25 years, are often kept in cold water aquariums.

The River catfish

The river catfish, is considered to be the largest freshwater fish in Europe. The catfish is particularly active at dusk and at night and feeds on dead and living fish, small mammals and water birds, and invertebrates. The catfish prefer to live in nature in large rivers and lakes, the bottom of which has a muddy bottom.

Typical of the catfish is an elongated body, while the head is wider. In addition, the European catfish has a stocky trunk in the front area that becomes slimmer towards the anus. In addition, the European catfish has large and powerful pectoral fins and an extremely small dorsal fin.

There is no typical coloration in the European catfish because the color adapts to the habitat of the respective animal, which means that the catfish is always excellently camouflaged. In most animals, however, the upper side is dark and has a gray basic color, which can vary in nuances from dark olive green to blackish, on the side the color of the European catfish is usually lighter.

Depending on where the European catfish lives, he can reach a body length of up to one and a half meters and a weight of up to 50 kilograms. However, catfish grow during their entire life, so that they can also become significantly larger.

The clown loaches

Loaches have their original habitat in the rivers of the Indonesian islands of Borneo and Sumatra. In order to be camouflaged as best as possible, these fish have black and orange body markings. Even if the loach is not a schooling fish in the classic sense, it still lives in its natural habitat in larger social groups that undertake their spawning migrations together.

The loach reaches a body length of about 30 centimeters and is extremely defensive against predators thanks to its eye thorns. Loaches are valued as a popular food fish in Indonesia. They live in groups and therefore form a territory in which they do not tolerate intruders.

The loach is generally a subspecies that is closely related to the carp. These aquarium fish mainly live on the bottom and appreciate it when they find plenty of opportunities to hide in the aquarium. The aquarium for loach should be dimensioned accordingly generously. Ideally, they should be kept in groups of eight to ten animals.

The jewel cichlid

The Lifalilis cichlid, which aquarium enthusiasts are more likely to know under the name jeweled cichlid, has its home in Central and Central Africa. It feeds mainly on insects, crustaceans, worms, small fish and plants. Whether it is a male or a female animal can be determined relatively easily based on the body shape; because male jewel cichlids are much stronger than female specimens and have a darker red color.

The jeweled cichlid, which can reach a body length of up to twelve centimeters, has been a popular aquarium fish since the 1970s. If you want to keep more than one pair, you should make sure that the aquarium offers enough space. The reason: jewel cichlids form territories that they defend aggressively.

This is especially true during spawning time. The perch defend the up to 500 eggs that they lay during spawning extremely vehemently. Even as soon as the offspring hatch, they are still closely guarded by their parents for a period of around two weeks.

Beginner Questions: Running in an aquarium after initial setup

37. What does running in an aquarium mean?

An aquarium is run in when the bacteria have multiplied so much that they break down so many pollutants that the pollutant content of the water remains harmless to the aquarium inhabitants between water changes. By feeding the fish, the fish droppings, etc. pollutants get into the aquarium water.

These pollutants harm the fish and lead to the death of the fish if there are too many pollutants. Certain bacteria break down some of the pollutants; some of the pollutants are removed by changing the water. In a freshly set up aquarium there are very few bacteria that break down pollutants.

38. How is the aquarium run in?

When setting up a new aquarium, the aquarium is completely set up, plants are inserted and water is poured in. The aquarium is put into operation without inserting fish.

Due to the decomposition of organic substances, e.g. dying plant leaves, ammonium is formed. Ammonium is absorbed by certain bacteria, which process the ammonium and finally excrete the nitrite, which is toxic for fish.

Nitrite is also absorbed and processed by bacteria, which in turn excrete nitrate. The bacterial species involved in each case only multiply if the required food, i.e. ammonium and nitrite, is available in sufficient quantities. The bacteria settle primarily in the filter, but also in the substrate.

During the running-in period, the nitrite value is measured daily. At the beginning the nitrite value is low, but increases slowly and steadily. The more the ammonium-degrading and nitrite-producing bacteria multiply, the faster the nitrite value increases. At the same time, the bacteria that break down nitrite receive more and more food and in turn multiply. After approx. 3 to 4 weeks so many nitrite-degrading bacteria have settled in the filter and in the substrate that they degrade more nitrite than is newly produced. The measured nitrite value begins to decrease.

As soon as no more nitrite can be determined in the daily measurements, the running-in is finished. From this point on, there are so many nitrite-degrading bacteria in the aquarium that there are no dangerous concentrations of pollutants if there is a weekly water change of approx. 30% water between the individual water changes. Nevertheless, the nitrite level should be monitored for a while.

If you take the trouble and measure the nitrate value at the same time, you will notice that after a while the nitrate value also rises. Usually this happens when the nitrite level starts to drop again. Up to a certain level, nitrate is desirable and serves the plants as a nutrient. Nitrate values ​​above 50 mg per liter are harmful.

It is recommended every now and then to put a few fish in the aquarium to bring in and then gradually increase the stock. The metabolism of the first fish or their excretions then stimulates the reproduction of the bacteria.

This method is only suitable for experienced aquarists who can quickly identify and react correctly if problems arise in the aquarium. Beginners should definitely pay attention to the running-in period and only insert a few fish after the running-in period in order to then increase the fish population step by step.

39. Which pollutants are produced in the aquarium?

The best known pollutant in the aquarium is nitrite, which is poisonous for fish. Even a nitrite value of more than 0.1 mg / L can damage fish. In addition, ammonia, which is even more toxic for fish, is produced at high pH values ​​of around 8. At values ​​below 8, the ammonia is partly converted into less toxic ammonium.

Nitrate can also be harmful if there are more than 50 mg / L in the water. If the pollutant levels are too high, the pollutant content must be reduced immediately by changing the water and brought into harmless areas. Ammonium and nitrate are partly consumed as nutrients by the plants. The substances are invisibly dissolved in the water.

40. How are the pollutants in the aquarium measured?

In the aquarium trade there are water tests with which the nitrite value and the ammonia value can be measured. The nitrite test is usually sufficient. If the pH values ​​are high, an ammonia test is useful.

41. Where do the bacteria in the aquarium come from?

Tap water is not completely sterile and contains a lot of bacteria. There are also numerous bacteria in the dust in the air, on all objects. They are spread through touch, air currents, breathing, etc. Bacteria are also found in sand or gravel. So many different bacteria come into the aquarium without any special intervention. The desired bacteria then multiply in the filter.

42. What do the bacteria that break down harmful substances feed on in fresh, clean tap water?

The tap water already contains nutrients for the bacteria. In addition, some flake food can be added to the aquarium to feed the bacteria. Leaves falling off the plants get more food for the bacteria into the water. Snails that may have entered the aquarium with the plants also produce food for bacteria.

43. What feed should I use during the running-in phase?

It is often recommended to add food to the aquarium every now and then during the running-in phase. As food for the desired bacteria, a very small pinch of finely grated flake food is put into the aquarium every 2 days. In this case, a lot doesn’t help much. Too much food starts to go moldy. Organic substances enter the aquarium through the food.

Not only flake food is suitable as a food source for the bacteria, but also also food tablets. The protein value is particularly important. Therefore frozen mosquito larvae, food granules and the like can also be used. The food should be rubbed as small as possible so that it dissolves quickly and no mold builds up. It is also possible to add some ammonium from the chemical trade or pharmacy directly to the water as a start-up aid.

It is unclear whether this method has any real advantage. Some aquarists are of the opinion that aquariums run in this way are much more stable than other aquariums. Other aquarists deny the effect. The running-in time is not significantly reduced. Systematic and meaningful studies are not known.

44. What is a nitrite peak?

If you enter the results of the daily nitrite measurements during the running-in period in a graphic or coordinate system (x-axis = days, y-axis = nitrite value), the result is a curve that rises slowly at first, then more and more steeply, which again after reaching a highest point falls off. The shape of the overall curve is similar to a bell or a mountain (a peak).

The highest point of the curve, i.e. the largest measured nitrite value, is the so-called nitrite peak. Since the maximum value differs depending on the aquarium, no absolute number can be given as the maximum value. However, the value can rise to more than 1 mg / L, i.e. to absolutely deadly values ​​for fish – Therefore, under no circumstances use fish before the successful entry.

A nitrite peak is analogous to an ammonium peak and a nitrate peak.

45. When an aquarium considered run in?

The aquarium is retracted when the nitrite value has risen and, after reaching a maximum value, has decreased so far that no more nitrite can be determined by measurements. During this time, food has to be added to the aquarium.

If the nitrite value does not rise, or if the value does not fall below the detectable limit again after reaching a maximum value, the amount of feed should be increased carefully. The bacteria may not be getting enough nutrition and are therefore not active enough.

Only when the nitrite value drops after a maximum value has been reached, despite feeding, and finally no more nitrite can be detected, the bacteria work as required.

46. How long does it take to run in an aquarium?

Experience has shown that it takes about 3 to 4 weeks to run in a newly set up aquarium. The increase in nitrite often begins after about 14 days. The nitrite peak is often between the 21st and the 24th day. After about 4 weeks, increased nitrite levels are usually no longer detectable.

In small aquariums, the nitrite peak can be between the 10th and 15th day. Other data assume approx. 10 days to the ammonium peak and approx. 30 days to the nitrite peak. Since the duration cannot be precisely predicted, without measurements it makes sense to wait 6 weeks until the first fish are introduced.

If the nitrite value is measured regularly during the running-in period, fish can be used if the nitrite value has dropped to zero after the nitrite peak has been reached.

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