Association of fish and large crayfish

Water values

Since the large crayfish common in aquaristics are nowhere near as sensitive to water hardness as shrimp, you have more options when selecting fish. In principle, however, most crayfish do not come from soft water with a low pH, they rather need hard water and a neutral to alkaline pH of 7 to 8. Soft water fish need other conditions, they should therefore better not be socialized with crayfish in the aquarium, because the requirements of the animals do not match.

To consider before socializing

Long-finned fish

Large crayfish have large claws and can develop tremendous strength. Fish with long fins, i.e. the veil forms of various aquarium fish such as guppies, danios, cardinalfish and fighting fish, but also long-finned species such as angelfish and gourami should not be socialized with crayfish in the aquarium. The crayfish pinches the fin and has the fish - and the fish is then normally not only injured, but eaten altogether. Even if the fish still manages to escape the crayfish, the wounds can become badly infected.

Bottom dwelling fish

Fish that sleep on the bottom like honey gouramis or some perch and tetra species or bottom-dwelling fish like gobies, Antenna catfish, other loricariids or armored catfish are also not suitable for crayfish. The nocturnal Cherax, in particular, like to help themselves to sleeping fish when they can get at them. Fish that inhabit the same habitat can potentially be nipped, with the consequences we described above.

However, there are also examples where socialization of Antennae Catfish and Crayfish can be done quite easily - crayfish are simply character animals, what works for one is guaranteed to go wrong for the other.

Predatory fish

It is also not advisable to keep aquarium crayfish with predatory fish. Predatory cichlids, such as some species of cichlids from Lake Malawi or Lake Tanganyika, will prey on crayfish, as will knifefish, large perch species, large gobies, and bony tongues such as the arowana. Even smaller species of predatory fish can severely injure young crayfish in particular, and with large crayfish it's the end of the line after molting at the latest: as long as the crayfish is still soft ("butter crayfish"), the predators have an easy time of it.

Special features of the aquarium setup

Crayfish do not like to sit on a plate - even in a species tank they need caves and shelters. Caution - many crayfish dig, so decorative materials should be placed so that they cannot tip against the aquarium glass or crush the crayfish if they are burrowed under. Plants have a hard time in the crayfish aquarium. They are dug up, partly also eaten or at least pinched off. Fish that like dense planting should therefore not be kept together with crayfish, because the aquarium with crayfish is likely to look rather bare sooner or later.

The aquarium size

When keeping crayfish, the size of the aquarium is important. Crayfish from the genera Cherax, Procambarus, Cambarus, Fallicambarus and so on become quite large depending on the species and need a correspondingly large and well structured base area, which not only offers space to run around, but also hiding places and visual barriers. For fish  in Germany, the expert opinion on the minimum requirements for the keeping of ornamental fish (freshwater) of the Federal Ministry for Consumer Protection, Food and Agriculture from 1998 is used. This document contains recommendations for the size of tanks for the various fish species, which should be adhered to except in the case of very small fish, if the keeping is only of a temporary nature or if the fish are kept for breeding purposes. At least 54 liters or 60 cm edge length is required, depending on the species even more. According to the Austrian Animal Husbandry Ordinance, aquariums with an edge length of less than 60 cm or a volume of less than 54 liters are not suitable for keeping fish.

For crayfish, however, 54 liters are already clearly too little for one animal, especially for the medium-sized to large species. In case of doubt: please plan more space than too little!

The fish - tetras

Various tetra species are a good choice for a crayfish aquarium. These fish are generally surface oriented and also quite nimble. They usually still escape well even with a crayfish that decides to go hunting. Since some species form territories, good structuring of the aquarium also suits them. However, tetras also need free swimming space, which can be set up quite well in a sparsely planted crayfish aquarium. Tetras are easily recognized by the small adipose fin they carry on their back. It sits between the dorsal fin and the caudal fin. Many tetras come from rather soft and acidic water - these species are then not quite as suitable for socialization with crayfish due to the different demands on the water values.

Tetras that can also be kept in somewhat harder water with a GH up to approx. 14 °dGH include the Congo Tetra, the Yellow Congo Tetra, the Red of Rio, Copper Tetras, the Red Phantom Tetra, the Roach Moenkhausia, the Star-spotted Tetra and several others. Tetras are group fish and should be kept in a larger school. They feed omnivorously, so they are omnivores.

Spikefish

Spikefish such as Boeseman's Rainbowfish and the Spotted Blueeye do well in harder water. However, they need weedy tanks, which can be quite difficult in an aquarium with crayfish. Here we recommend the use of fast-growing robust floating plants such as nixweed, waterweed or hornwort. Plants floating on the water surface, such as frogbit or shellflowers with their long hanging root tufts, also provide cover for the fish.

Livebearing

The same planting principle can be applied to a community aquarium where crayfish live with livebearers. Guppies, Endlers, Platies or Swordtails are a perfect match for crayfish in terms of their water hardness requirements. These species reproduce very strongly, so it does not matter much if the crayfish catches a careless fish.

Carp and rice fish

Smaller egg-laying toothcarps, for example Norman's shining-eye fish or also pike-fish fit from the water values into an aquarium with crayfish. However, they also prefer weedy tanks, which should be taken into account with fast growing plants as described above for the spikefish.

Dwarf danios and barbs

The same is true for danios and barbs. Many danios prefer soft and rather acidic water, but for example guinea fowl danios and cross stripe danios like harder water. The zebra danio also fits in an aquarium with crayfish. Barbs like the splendid barb or the sumatra barb are also suitable. Despite the horticultural activities of the crayfish in the aquarium, sufficient planting should also be ensured for danios and barbs.

Loricariids and dwarf armored catfishes

Socializing catfish and crayfish can go well, but conflicts are pre-programmed in many cases due to the shared habitat. We do not recommend keeping crayfish and bottom-dwelling fish together.

Cichlids

Many cichlids are predators and like to eat freshly skinned crayfish or young crayfish. A socialization can go well for example with Mbunas like the Pseudothropheus or Cynotilapia, which feed on plants and growth. In the cichlid aquarium crayfish need in any case many hiding places, which must be such that the cichlids can not get into the caves.