General information about freshwater shrimp
Stores usually offer (native) European crayfish, Gammarus, as freshwater shrimp. Central American or Mexican amphipods, Hyalella azteca, are often referred to as freshwater amphipods on the internet.
European freshwater shrimp
Freshwater Crayfish Photo: Nadine Szperalski
European freshwater shrimp, Gammarus, can be found in most streams that are not yet too heavily polluted. 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 located there are caught. A few minutes of practice are required.
European freshwater shrimp need a lot of oxygen and need quite low temperatures. Temperatures above 28° are poorly tolerated without ventilation. With additional ventilation through an oxygen stone or stronger flow, they can also withstand very high temperatures in summer.
In summer, the animals should possibly be kept near a basement window facing north or east, as they need oxygen and cooler water can absorb more oxygen.
Breeding of freshwater shrimp
Freshwater Crab Photo: Nadine Szperalski
A container slightly larger than a mason jar is suitable for breeding. Some substrate and soil mulch is filled into the basin. Java moss can be added to the tank. After the break-in, breeding can begin.
The breeding tank should have a weak to good flow. Temperatures should be low. Green water is not necessary because European freshwater shrimp are not filter feeders. The water should not turn green.
Fully developed young hatch from the eggs. They find food in the form of mulm, algae, decaying plants, carrion and fish droppings.
All types of plant food are suitable as food, including slices of cucumber or similar. Because the decomposition of food can quickly use up the oxygen in the tank, you should not feed too much.
Central American Freshwater Crabs
Central American amphipods, Hyalella azteca, are easier to keep than European freshwater amphipods. The crabs are about 1 centimeter in size. They can be kept and propagated in 2 liter cucumber jars that are heavily overgrown with algae. But then they remain smaller than in larger tanks.
Either coarse substrate or, even better, a layer of snail shells is suitable as a floor. They like to hide in it and probably also prefer to reproduce there.
Breeding of Central American Freshwater Crabs
Freshwater Crab Photo: Nadine Szperalski
A normal aquarium measuring 30x20x20 cm or larger is suitable for breeding. Small 12 liter tanks can also be used. A cover is not necessary. The tank can be planted with riccia, java moss, tomentosum, pondweed and Cladophora balls (moss balls). A slight aeration can provide some water movement. In a well-planted tank, however, a flow is not absolutely necessary because the crabs do not need much oxygen. The temperature should be between 20 and 26°C. 25° is most suitable. Constant temperatures below 15° are unsuitable.
A 50x10x30 cm plastic bowl filled with pond water is also suitable. The bowl can, for example, be placed on the balcony if the weather is not too cold. In cold weather, the bowl can be placed in a room at normal room temperature.
A few small snails can also be placed in the container to eat excess food.
Water should be changed about 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 have a predominantly vegetarian diet. This may be the reason for their preference for Riccia, which forms tasty shoots at all ends. However, the crabs do not reduce the plants.
Suitable feed:
- lettuce leaves
- cucumber slices
- dried animal food
- Yeast
- dry yeast
- Spirulina Algae
Apparently, sweets such as mangoes, halved grapes, rotten banana slices or canned carrots are eaten with pleasure.
According to some reports, the crabs occasionally eat meat, such as balls of ground onion.
Central American freshwater shrimp as fish food
Many aquarists do not keep Central American freshwater shrimps for food breeding, but because the owners like them. Other aquarists keep the crabs as a food reserve in the aquarium, i.e. not in an extra tank for breeding, e.g. to bridge longer absences. For regular feeding, a lot of crabs are needed, which can only be raised in really heavily algae-covered, green tanks.
Not all fish eat the freshwater shrimp. The crabs usually like to eat larger fish, such as labyrinth fish, livebearers, barbel, goodeids and cichlids. Small fish, such as dwarf rasboras, tend not to eat the crabs. Armored catfish and thorn eyes don’t seem to be interested in freshwater shrimp
Produce green water with algae
A 10 liter photo tray is placed on a windowsill with morning sun. The bowl is filled with a thin layer of sand and reverse osmosis water. Then a pinch of Triops eggs is added to the shell. After some time, the triops hatch.
When the triops get bigger, so much dirt accumulates that single-celled algae thrive. Filamentous algae are grazed by the triops.
In this way, green water for the water fleas can be harvested almost regularly for several months. However, the crabs do not appear to be dependent on green water. They can multiply quickly even without green water.
Mexican freshwater shrimp, snails and shrimp
Mexican freshwater shrimp often use empty snail shells as shelter. Either because usable mulm collects there, or as cover for laying eggs. They can also be found in coarse gravel and filter sponge.
Crayfish have also been observed to crawl into the shells of live ramshorn snails. No negative effects on the snails were observed.
Because freshwater shrimp sometimes seem to eat meat, their behavior towards dwarf shrimp eggs and snails should be monitored. According to a report, numerous freshwater shrimps swam up to 4 knobbed tower snails that had just been placed in a tank. The snails withdrew completely into their shells. The snails were then removed from the tank. 2 snails later turned out to be dead. It is unclear whether the snails were dead before they were introduced, were killed by the freshwater shrimp, or died later.
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