If you are going to have a pet crayfish, there are a few things you might want to consider. After having a pet crayfish for almost three years, I have learned several important things about pet crayfish care.
Tank Size Matters
First off, tank size is going to be pretty important if you plan on having a crayfish and other fish. For one, crayfish are very dirty creatures. A crayfish can dirty up a tank rather quickly by the waste it produces. For this reason, I'd suggest at least a twenty gallon tank. Personally I've been able to keep my own crayfish in a ten gallon tank. However, doing so required more frequent water changes in order to keep the tank looking fresh and clean.
Also, a larger tank will provide more room for your crayfish and other fish. This is good as crayfish are very territorial creatures.
Types of Tank Mates
Crayfish are aggressive creatures. They are omnivores who love nothing more than getting their claws on something and eating it. They have no problem eating other the fish in your tank, the plants and even other crayfish, if you have them.
So if you plan on having other fish in your fish tank along with your pet crayfish, get fish who are also aggressive. Fish that swim near the top of the tank and who are fast work great too.
Currently I have hatchet fish and a red tail shark in my twenty gallon tank along with my pet blue crayfish. The red tail shark has actually been living with my pet crayfish for about two years. It's worked out very well because he too is aggressive, swim near the top of the tank and is a fast swimmer. This does not mean that my crayfish does not try to snatch him up from time to time, he does.
Remember, fish who are slow and swim near the bottom of the fish tank, where crayfish dwell, are very likely to be ateen. I have lost a few fish early on because they were slow-swimming fish.
My experience has been that if I keep my crayfish fed well, they are not always as aggressive. Obviously, the more hungry a crayfish is, the more likely it is to try to hunt down and capture your other fish. So keep your crayfish fed, but of course do not overfeed him.
Get a Hideout
Your crayfish needs a hideout. Again, crayfish are territorial and like to have a place to burrow. This is especially true and important when your pet crayfish molts. Because when a crayfish molts, he too becomes a target to other creatures in the tank, as he is weak. Hideouts are cheap and can be purchased at any pet store. Or you can simply make them out of PVC pipe.