River flea shrimp in the aquarium

River flea shrimp

Uses and different types of river flea shrimp for your aquarium

There are two river flea shrimp species:

  • Gammarus pulex
  • Gammarus Fossarum

They both have slightly different requirements in terms of water quality, substrate and flow conditions, but also occur together over long stretches of water.

Since they can hardly be distinguished from one another externally, they are normally discussed together.

River flea shrimp: General information

The same framework conditions apply to the keeping and breeding of the river shrimp in the aquarium:

  • Clean, oxygen-rich water with sufficient lime content
  • A pH value > 7

The river flea shrimp use fallen leaves, detritus and ground mulm as a source of food, as well as the commercially available dry food for ornamental fish.

Before the brown shrimp mate, they often swim piggyback through the aquarium for weeks in a precopular position. The number of eggs per clutch of the river flea shrimp is relatively low, but the rate of successfully hatched young shrimp is quite high because they can develop in the protected breeding space of the females.

River flea shrimp: Spread and habitat

The river flea shrimp is widespread in Europe and also occurs in northern Asia as far as China.

In the south-west of Europe, on the Iberian Peninsula, it is absent. Here, its ecological niche in the rivers and lakes is partially replaced by Echinogammarus berrilloni (which, however, is already a newcomer to us in Central European waters), replaced by Gammarus italicus.

Conversely, the river shrimp was introduced into Irish waters, where it now displaces the native Gammarus duebeni.

Also in the Rhine and ultimately also in Lake Constance, new invasive Gammarus species are increasingly appearing, some of which migrate upstream of the Rhine, some of which are brought in as stowaways in pleasure craft. One subspecies, Gammarus pulex cognominis, inhabits underground waters.

The main distribution of the Gammarus pulex river flea shrimp is in Central Europe in the streams of the plain, upstream it becomes of the Gammarus fossarum river flea shrimp from an altitude of about 400m above sea level. NN replaced. However, both species can also occur together over long stretches of flow and form mixed populations. In general, the Gammarus pulex river flea shrimp is somewhat more wastewater-tolerant and adapted to lower oxygen concentrations. This is also reflected in the saprobic system: Here the Gammarus Pulex river flea shrimp has a significantly better quality index with 2.0 than the Gammarus fossarum river flea shrimp with 2.5 on a scale from 1 for very good to 4 = poor water quality.

If both species occur in the same stretch of water, the Gammarus pulex river flea shrimp seeks the less current microhabitats near the bank, while Gammarus fossarum river flea shrimp are more likely to be found in areas exposed to the current. In the upper reaches of the rivers, the trout zone, both gammarid species, along with mayfly larvae, often make up the largest proportion of macroinverebrates living on the water floor.

Settlement densities of up to 10,000 individuals per square meter were found. Gammarids can be found in large numbers, especially where the autumn leaves accumulate in the stream. They are less interested in the fall foliage themselves than in the growth of microfauna and flora that forms when the leaves decompose.

Both species of river flea are very sensitive to the acidification of the waters caused by humans. They die or stop growing at a pH value of 6.0. In an acidic and thus lime-poor environment, the river flea shrimp have difficulties with the formation of the chitin-containing exoskeleton after molting.

In boggy waters, the mortality of the river flea shrimp is somewhat reduced by the buffer effect of the humic substances carried in the water. The species is therefore more common in calcareous waters, it is absent in naturally acidic waters such as Bog waters.

Gammarus pulex in aquarium

River flea shrimp: Features, shape and color

  • The body is compressed to the side and the river flea shrimp usually swims on its side.
  • The head is fused with the first breast segment to form the cephalothorax, but the other segments are exposed because amphipods do not have a back armor, called a carapace.
  • The eyes of the river flea shrimp are sessile and embedded in the head.
  • The extremities in the chest area do not have webs of webbed feet: the first pair of legs is converted into jaw feet, the others have gills.
  • The jaws are followed by 4 pairs of legs, which form forward-facing grasping legs with claws turned backwards.
  • The other three pairs of legs are designed as simply rearward-facing clamp legs. The extremities of the abdomen also show a similar dichotomy (Amphipoda = two kinds of feet). The first three pairs represent row legs densely occupied with long hairs, followed by stylized uropods pointing backwards, which function as spring legs and pushers.
  • Equipped with extremities in this way, the river amphibians are able to walk nimbly over the soil substrate in a lateral position and to defy the current, as well as to swim freely through the water.
river flea shrimp
River flea shrimp

River flea shrimp: In the aquarium

  • Gammarus pulex and fassoarum are dependent on cooler water temperatures. The aquarium should be set up in a relatively cool room that is barely heated by the sun.
  • Good ventilation and oxygen supply are important. A planting like the one for the Gammarus roeseli aquarium is not enough to provide oxygen.
  • In addition, a diaphragm pump and air stone must be used for ventilation and further oxygen entry into the water.
  • A well-functioning filter system is also important.
  • The water should be medium hard to hard and rich in calcium and be in the slightly alkaline range (pH> 7). Since the river shrimp, unlike the river flea shrimp Gammarus roeseli, are not an intermediate host for the parasite Polymorphus minutus, which is dangerous for fish, the river shrimp can also be safely removed from a river to set up their own aquarium breeding.
  • As a source of food, the river fleas are fed autumn leaves and detritus in the aquarium.

River flea shrimp: Breeding

In order to match the timing for successful fertilization, the larger male stream flea shrimp cling to the back of the female and often swim back and forth in the aquarium for weeks with this piggyback in the side position. Because they wait in order to be able to copulate with the female and fertilize the eggs, the next molting phase.

Only then is the female’s freshly skinned exoskeleton thin enough. If both species of river flea shrimp are kept together, confusion and mismatches between Gammarus pulex and G.fossarum can occur, from which, however, no offspring can result.

Amazingly, these pairs, connected to one another in the so-called precopular phase, are just as active and swim in elegant arches across the aquarium as the individual animals. For fertilization itself, the male releases the female from its grip, turns towards the female’s belly to release sperm there.

The fertilization takes place externally with the river flea shrimp. The eggs are not placed in the water by the female, but rather, as can be observed in the crayfish, carried along in a brood pouch on the belly side. The eggs are initially surrounded by a gelatinous shell which, however, dissolves over time. The number of eggs in clutches is between 15 and 30, in younger females it can also be less. Each female stream flea can reproduce three times a year. River shrimp live only 1 to 2 years old.

After a gestation period of around 3 weeks, the young hatch and are protected in the females’ brood chamber for a few more days before they are released into the open water. At an average room temperature of 20 degrees Celsius, they are sexually mature after 11 to 12 weeks, at lower water temperatures it can take much longer. Additionally, the river shrimp usually only reproduce in the summer months.

Mating Gammarus pulex

How to breed river flea shrimps

  • First set up a suitable container that is slightly larger than a mason jar.
  • Fill in some soil into the basin.
  • Add Java moss to the tank. After running-in, breeding can begin.
  • Make sure that the breeding tank has a weak to good flow.
  • Set low temperatures.
  • Green water is not necessary because European river amphibians are not filter feeders. The water shouldn’t turn green.
  • Young hatch will develop from the eggs.
  • They find food in the form of sludge, algae, decaying plants, carrion and fish droppings.
  • All kinds of plant-based food are suitable as feed, including cucumber slices or similar. Because the decomposition of feed can quickly use up the oxygen in the tank, you should not feed too much.

River flea shrimp: Suitable feed

  • Lettuce leaves
  • Cucumber slices
  • dried animal food
  • yeast
  • Dry yeast
  • Spirulina algae

Apparently, people like to eat sweet things like mango, halved grapes, battered banana slices or canned carrots.

According to some reports, the crabs also eat meat from time to time, for example balls made from onion meat.

River flea shrimp: As food for other fish in the aquarium

River flea shrimps are dried, valuable, natural and pure natural food to supplement the feeding of koi or pond fish and large aquarium fish.

  • It is a rich source of energy.
  • Ideal complementary feed to fish feed and substitute for live and frozen feed.
  • Gammarus swims on the surface for a long time and never tarnishes the water.
  • Is eaten by all fish, even small ones, as the river flea shrimp can be easily grated and chopped by hand.
  • The carotenoids contained in it allow the natural colors to develop fully.
  • In addition, they are full of minerals and vitamins that are fully preserved through gentle freeze drying.
  • The fiber content ensures good digestion.

River fleas contain nutrients, vitamins, minerals, trace elements and pigments, the bioavailability of which corresponds to the natural food of the koi. They were dried while largely preserving the ingredients.

From unpolluted, cleanest brooks in Belarus.
We can guarantee quality and freshness through direct import.

The delicacies can be made available to the other fish from a water temperature of 11 ° C.
The contained natural fiber promotes the digestion of the given main feed.

Our tip:
plan one day a week on which you only feed freshwater shrimp. This allows the intestine to regenerate.

Ingredients *:
Crude protein: approx. 48%
crude fat: approx. 3%
raw fiber: approx. 4.6 % crude
ash: approx. 4.6%
moisture: approx. 1.9%

European River flea shrimp

European river flea shrimp, Gammarus, can be found in most of the not yet too polluted streams. For this purpose, a net is held to the ground behind a stone in the direction of flow. Then the stone is turned over and the crabs there are caught. A few minutes of practice are required.

European river flea shrimps are much oxygenated and need very low temperatures. Temperatures above 28 ° are poorly tolerated without ventilation. With additional ventilation through an oxygen stone or a stronger current, they can withstand very high temperatures in summer.

In summer the animals should possibly be kept at a cellar window facing north or east, as they need oxygen and cooler water can absorb more oxygen.

Central American River flea shrimp

Central American river shrimp, Hyalella azteca, are easier to keep than European river shrimp. The crabs are about 1 centimeter tall. They can be kept and propagated in 2 liter cucumber jars with strong algae. But then they stay smaller than in larger pools.

Either a coarse substrate or, even better, a layer of snail shells is suitable for the soil. They like to hide in them and probably reproduce there preferentially.

Breeding Central American River flea shrimp

A normal aquarium measuring 30x20x20 cm or larger is suitable for breeding. Small 12 liter basins can also be used. A cover is not necessary. The basin can be planted with riccia, java moss, hornwort, pondweed and cladophora balls (moss balls). Slight ventilation can provide some water movement.

In a well-planted tank, however, a flow through is not absolutely necessary because the crabs do not need very much oxygen. The temperature should be between 20 and 26 ° C. 25 ° are best. Permanent temperatures below 15 ° are unsuitable.

A 50x10x30 cm plastic bowl filled with pond water is also suitable. The bowl can, for example, stand on the balcony when the weather is not too cold. In cold weather, the bowl can be placed in a room with normal room temperature.

A few small snails can also be placed in the vessel to eat excess food.

The water should be changed approximately every 3 weeks. The water can be cloudy. The more polluted the water, the faster the crabs seem to multiply. Water that is too clean inhibits reproduction.

Hyalella azteca are predominantly vegetarian. This may also be the origin of her preference for Riccia, which forms tasty shoots at all ends. However, the crabs do not reduce the plants.

Central American river fleas as fish food

Many aquarists do not keep Central American river shrimp as fodder, but because the keepers like them. Other aquarists keep the crayfish as a food reserve in the aquarium, i.e. not in a separate tank for breeding, e.g. to bridge longer absences. A lot of crabs are needed for regular feeding, and they can only be raised in really heavily algae, green tanks.

The river flea shrimp do not eat all fish. Larger fish such as labyrinth fish, livebearers , barbels, highland parsons (goodeids) and cichlids are usually eaten by the crabs. The crabs tend not to eat small fish, e.g. dwarf grass boras. Armored catfish and thorn eyes do not seem to be interested in river fleas.

Mexican river flea shrimp, snails and prawns

Mexican river fleas often use empty snail shells for shelter. Either because reusable sludge collects there, or as a cover for laying eggs. They can also be found in coarse gravel and filter sponge.

Crabs have also been observed to crawl into the shells of live ramshorn snails . Negative effects on the snails were not observed.

Because river flea shrimp seem to eat meat every now and then, their behavior towards dwarf shrimp eggs and snails should be observed. According to a report, 4 nubby tower snails newly placed in a basin were swum by numerous river flea shrimp.

The snails completely withdrew into their shells. The snails were then removed from the tank again. 2 snails were later found dead. It is unclear whether the snails were already dead before they were introduced, whether they were killed by the river fleas or whether they died later.

Generate algae-rich, green water

A 10 liter photo bowl is placed on a windowsill with the morning sun. The bowl is filled with a thin layer of sand and osmosis water. Then a pinch of Triops eggs is placed in the bowl. After a while the triops hatch.

When the Triops get bigger, there is so much dirt that single-celled algae thrive. Threaded algae are grazed by the Triops.

In this way you can harvest green water for the water fleas almost regularly for several months. However, the crabs do not seem to be dependent on green water. They can multiply quickly even without green water.

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