Shelters for crayfish in the aquarium.
Various decapods build more or less sophisticated burrows in nature, where they spend a significant part of their lives. Crayfish use their claws to dig burrows in the slopes of river and stream banks. In the aquarium, crayfish must have their own shelters where they will feel comfortable and safe. When keeping several individuals together, the lack of a sufficient number of shelters will lead to conflicts. Crayfish are awake at night, while during the day they spend most of their time in dark, secluded places. It is important that every crayfish has its own shelter.
The number of shelters in the aquarium should be one and a half times greater than the number of crayfish claiming these shelters. Immediately after molting, a crayfish is most vulnerable and can remain in a shelter for a long time. If the aquarium is overcrowded with crayfish or if there are not enough shelters, they will try to climb out, attempting to escape the aggression of larger relatives. For adult crayfish, shelters can be ceramic tubes, coconut shells, flower pots, etc. Young crayfish hide in thickets of fine-leaved aquarium plants.
Thanks to the rich imagination and skillful hands of amateur aquarists, we have examples of homemade shelters for invertebrates that can be used in your aquarium. In addition, manufacturers of aquarium accessories produce various shelters for crustaceans, which not only serve as homes but also possess other useful properties.
Stones. All kinds of intricate shapes, with depressions and “passages” in them, can be found yourself or bought in a store. If you find a suitable option in nature, before placing it in the aquarium, it is imperative to rinse it well, and even better, boil it to destroy pathogens on it. Very importantly, the stone is placed on the glass bottom of the aquarium, not on the substrate, as some crustaceans like to dig shelters in the substrate under stones. If the stone suddenly settles, it will lead to adverse consequences for the inhabitant hiding under it. The arrangement of stones in the aquarium should reproduce natural conditions.
Driftwood, tree branches, intricate roots, pieces of wood. Wooden shelters are one of the favorite homes of crayfish. The more intertwined the branches, the more passages and exits, the more suitable such a house is for arranging a community. Again, driftwood already prepared for placement in the aquarium can be bought in specialized stores. You can also prepare it yourself.
Fragments of flower pots can be used as houses. Crayfish like to settle in caves made of pot shards. The pots must be ceramic, not plastic, 
the smaller, the better. Crayfish feel safer if the entrance to the cave is narrow enough. Plastic pots should not be used, as the plastic they are made of can be toxic. They must be new, not used for indoor plants. The fact is that the microcracks of the pot may contain microorganisms living in the soil that are undesirable for the aquarium. And one more thing. Making properly shaped houses from whole pots is not just breaking a pot. Using a chisel and a hammer, two vertical and one horizontal cracks are made in the pot where the entrance to the cave will be. After “removing the door”, the sharp edges are treated with sandpaper or a file.
An excellent alternative to pots, although hard to get, is clay pipes. They are hexagonal on the outside, their inner section is round, and many bottom-dwelling fish really like them. However, clay pipes and pots have one drawback — if there are too many of them, they can release excessive amounts of aluminosilicates into the water. To protect yourself from this, it is enough just to boil the pots in a saturated peat decoction — they will darken, and the acids contained in the peat will bind undesirable substances.
If you have nowhere to get clay pipes, you can use pieces of plastic pipes for drinking water supply as an alternative. They come in different diameters, and since, for example, crayfish do not like large pipes, it is easy to pick something narrower for them. Pieces of old thick bamboo fishing rods can also be used to build several small-diameter tubes. By the way, if desired, dry bamboo can be scorched with a blowtorch or gas burner. Then beautiful dark stains will appear on it.
Another natural material for making a crayfish house can be a coconut shell cleaned of pulp. Break the nut in half crosswise. Then use an electric saw to cut out the doors. The “hair” on the nut can be left for decorative purposes, or removed and the surface sanded with sandpaper. A house prepared in this way can be lowered to the bottom as is, or decorated on top with moss, which will weigh down the shell. Shelters should have a minimum diameter of 15 mm and a depth of at least 4 cm. Empty snail shells are suitable for young crayfish.
Keeping freshwater crayfish in an aquarium. 
