Saltwater Aquariums Guide for Beginners

Saltwater aquarium

Have you been thinking about getting a saltwater aquarium? Or are you thinking about converting your freshwater aquarium?

There are a lot of freshwater aquarium owners who would love to switch to a saltwater aquarium. “Is it too complicated? How expensive is it?” are some of the questions that often are raised regarding the issue.

The reality is; switching from a freshwater to a saltwater aquarium is very easy especially when you have

  • robust, inexpensive and beautiful inhabitants animals
  • simple corals for your tank

Saltwater aquariums have been proven to have a calming effect on adults and children.  They are beautiful to look at. All you need are a few tips and tricks it can really bring joy into your home.

A General Introduction to Saltwater Aquariums

Aquarium tank

A saltwater aquarium can use any size tank. It is easier to start with about 250 liters. 

Just like in freshwater tanks, the following basics apply to saltwater aquariums:

  • The larger the pool, the more stable the cycle of life in it
  • The saltwater aquarium can also be created from an old freshwater aquarium.

Protein skimmer

A protein skimmer absorbs protein (mud) in the basin, and reduces permanent water changes or the “cleaning”. A protein skimmer is usually only required if fish are used.

Heating rod

A saltwater aquarium requires water regulation in order to achieve the desired temperature. 

Just like with most freshwater aquariums, the optimal temperature is around 25 degrees.

UV lamp / ozone device

A UV lamp can be used for very sensitive fish or sick fish. 

This can kill unwanted germs and thus “clear” the water. 

Using a filter basin is very practical – light in, shut the flap, germs dead.

Calcium reactor

You only have to have a calcium reactor if you want to keep large amounts of hard corals. It supplies the corals with sufficient natural lime and can be integrated into the filter tank.


For certain animals in saltwater aquariums, light play a very important role. For a majority of other animals it plays less of a role. 

You should consider investing in Led systems. 

Alternatively, T5 or T8 lighting systems, similar to those used in freshwater aquariums, are sufficient for certain animals such as anemones and soft corals.


There are various filter techniques and systems.

In principle, a saltwater aquarium can also run with an existing external filter (freshwater). 

The content of the filter is exchanged accordingly with materials from seawater aquariums.

A so-called filter basin is common in seawater aquariums. It sits under the aquarium and where you can place a large open filter made of glass. The advantage here is that you can pack all the technology down so that you don’t have too much of it in the aquarium. 

Here again it is crucial to consider which animals you will have in the aquarium. 

If it is corals, for example, that need completely clean water, then such a filter tank with several chambers (with various filter materials, protein skimmers, UV lamps, etc. are located) is recommended.


You can use with natural seawater or synthetic water in a seawater aquariums.

The water that evaporates is replenished with osmosis water. For the extraction of osmosis water there is a special filter (osmosis system) which is connected to the usual tap. 

Alternatively, you can simply get your osmosis water from a reputable store that sells natural seawater from the sea. This will save you time and space in the aquarium.

Saltwater Aquarium Ecology

Actors that support the ecosystem of a saltwater aquarium

The saltwater ecology is made up of three components:

  • Producers that use light energy and water
  • Consumers that depend on the biomass of other organisms
  • Destructors depend on the mineralization the biomass from the other 2 components

The above function to keep the ecosystem healthy:

  • The producers live from “light and air”, water and some minerals by using light energy and water to convert the carbon dioxide (CO2) contained in the environment into carbohydrates (sugar, starch, cellulose) so that they operate their own metabolism and Build up biomass. So they produce organic material, hence the name producer. This “job” is carried out by some bacteria as well as by all algae and other plants. As a “waste product” of photosynthesis (this is what the process of building up matter using light energy is called), oxygen (O2) is produced.
  • The consumers live from the producers or other consumers. They get their nutrients by consuming the biomass of other organisms. During their metabolism, oxygen (O2) is consumed and carbon dioxide (CO2) is given off. All animals, most fungi and many bacteria have this “job”. Those animals and fungi that feed on the excretions, waste and dead bodies of the producers and consumers are also consumers, but lead over to the destructors.
  • The Destructors after all, all that biomass from the other two “professions” is broken down into the starting materials: water, minerals and carbon dioxide (CO2). This process is also called mineralization, and it is mainly carried out by various bacteria and some fungi.

We come full circle, because water, minerals and carbon dioxide are the starting materials for producers.

Carbon and oxygen balance in the saltwater aquarium

The metabolism of the aquarium animals consumes oxygen (O2) and creates carbon dioxide (CO2).

CO2 accumulates in the water and, if the concentration is too high, leads to respiratory problems and acidification of both water as well as the blood of the fish. (Over-acidification because part of the CO2 dissolved in liquids reacts with water to form carbonic acid – we know this from mineral water.) This and the lack of oxygen (O2) lead to illness and death in fish and other animals. O2 deficiency can continue to promote putrefaction in the pool.

A strong ventilation of the water (i.e. an exchange of gas between the aquarium and the ambient air) can drive out the carbon dioxide from the water and bring in oxygen.

The nitrogen balance of the saltwater aquarium

The bacteria that cause nitrification (ammonium to nitrite to nitrate) live bound on

  • The substrate
  • On plant surfaces
  • On stones and glass walls
  • Between algae
  • In sludge

If you have a densely packed saltwater aquarium with inhabitants, you can and should increase their settlement area many times by offering them a flow-through.

This will ensure that O2 and nutrients are degraded and transported with the appropriate filter material.

How to make saltwater for aquariums in 5 easy steps

If you decide to mix the saltwater yourself, you will need to mix:

  • Osmosis water – either buy it or use a reverse osmosis system
  • Special sea salt mixture for aquariums
  • Clean bucket
  • Aquarium heating element
  • Small flow pump
  • Refractometer or hydrometer to measure the water density
  • Anything to stir (large spoon, scoop, etc.)

Step 1

Fill the osmosis water into a large bucket and bring it to a temperature of about 20 ° C with the help of the heating rod. 

When the temperature is reached, remove the heating element from the bucket (safely!)

Step 2

Now start to stir in the sea ​​salt slowly and evenly. A rough indication of how much you need is usually on the package of your salt.

Regularly test your water with the refractometer to see how high the specific density is. The specific density is an indirect value to determine the salinity of the water. Seawater has a salinity of 35ppt, which at 20 ° C a density of 1.025 corresponds.

A good guideline value for our density is 1.025, definitely not more.

Tip: Measure exactly how much salt you use to get the right value, then you will know pretty much exactly how much you have to use next time and you can save step 1.

Step 3

Once you have reached the density of 1,025, attach the flow pump in the bucket and turn it on. 

Try to adjust the flow in such a way that the water surface moves strongly – this ensures good gas exchange with the room air. 

Now place the heating rod in the bucket again, set it to the water temperature of your aquarium and turn it on. 

Step 4

Let the water stand for at least 20 hours so that the salt can spread out well. 

If you have poured the salt directly into it, the water values ​​can fluctuate very strongly in the next few hours, the water “matures” so to speak.

Step 5

Test the specific gravity again the next day. You will be amazed by how much the value can change in the first few hours. 

Now correct the density by adding either more salt or more osmosis water. Then let the water stand and “draw” again for a few hours.

As soon as the density is the desired value and the water has the same temperature as your pool, you can fill the water into the pool and use it. Finished!

How to set up a saltwater aquarium

How To Setup A Saltwater Aquarium: Step By Step

How to choose the right saltwater aquarium

Which Type Of Aquarium Should I Choose? | Beginner Guide To Saltwater Aquariums

How to maintain a saltwater aquarium

A saltwater aquarium requires less maintenance than a freshwater aquarium because the entire plant care with fertilizing and trimming the plants is omitted.

In the saltwater aquarium, the regular partial water changes and the addition of trace elements and calcium / magnesium are the main care. It is important to check the salinity with a hydrometer, as the salinity increases slowly due to water evaporation.

Every day maintenance

  • The animals (corals and fish) can be fed using the automatic feeder
  • Refill water depending on evaporation, possible automatically by means of an automatic refill

Weekly maintenance

  • Droplet test, the important elements (KH Nitrate MG CA) and, if necessary, re-dose
  • Cleaning the protein skimmer, if present
  • Clean the windows

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