Crayfish need a tank with a pH of 7.0 (neutral) that has a temperature between 70–75 °F (21–24 °C). Do not use a heated aquarium for these critters. Additionally, the aquarium should have proper aeration and filtration. One crayfish needs at least 5–10 gallons (18.9–37.9 L) of water all to himself.[2]
It's not recommended that you put more than one crayfish in a tank, but if you do, you should make sure they have enough space to themselves, and enough places to hide. Also, if you do have multiple crayfish in one tank, make sure they are of the same species, or they are likely to kill each other.
In addition to filter oxygenation, you'll need air bubblers or long bubble walls on your tank.
Make sure to partially change the water each week to keep it fresh.
You can also put your crayfish in a tank with fish, if you take the right precautions -- more on that later!
Don't put seashells in the tank, or this can affect the pH level of the water.
Perform regular water changes. Because crayfish have large bio-loads, do at least two water changes each week. Always use a dechlorinator when replacing water.
Don't use an undergravel filter. Crayfish like to dig, which can jam the filter.