Try doing a search on this site, i know crayfish have come up lots. Blue crayfish are cared for the same way as regular crayfish.So any info you find on brown/red crayfish will work also for hte blues.
If you plan on keeping one I wouldnt' recommend keeping it with fish.
also they are spendy for something that lives three years from birth.If you chose one get the smallest one you can find.
They WILL pick off small fish one by one.
I have blues that I purchased from Bob at bluecrayfish.com at reasonable prices even with shipping. Bob is really great! And, it's true, they are pretty formidable predators, but they CAN be kept with fish, depending on size and/or speed.
I have a 3 inch female in a 10g with 3 paradise fish (a male and 2 females). Not only does she not bother the fish, they will often inhabit the same cave with no ill effects. As a matter of fact, I have to feed the paradise fish flake food or bloodworms before I drop her her shrimp pellet, otherwise they fight over it - often with the male paradie fish the winner! HOWEVER, when I first got the blue she did kill and eat a blind cave tetra, but I think that it probably blundered into her, being blind and all. She also snacked on a white cloud that was listless and possibly dying.
I also have a slightly smaller male in a 10g (a different one) and he has happily resided with a small school of mixed white and gold clouds, and the "survivor" cave tetra for several months.
The biggest concern is actually that the blues require cooler temps than most tropical fish. No heater. However, many tetras and danios have safe temp ranges that overlap the blues' safe temp ranges.
I had one he got about 4 1/2 5 inches and didnt touch anything in my tank , every time he molted got darker blue he stopped eating flakes and we fed him some meat from that nights meal (the bad parts of the meat ) but otherwise he was great and lived longer than 3 years.)
I think they live longer than 3 years, too. I had one that grew big enough that he could have filled dinner a plate quite nicely.
He would eat any fish he could catch, and he caught them all.
One thing to be aware of - they like to go on walkabout. Mine got out three times and used to terrorize the dogs. He finally got out one day when I wasn't home. I found him 20 ft away from the tank. I think he could have made it but the dogs took their revenge.......
Have you seen the "snow white" crayfish? They are really something to look at, I'd spring the extra cash for one of those if i was setting up another crayfish tank. Anyways I've had my blue for about a year and a half. Hes molted twice and gotten bluer each time. He has never killed a fish, but i have left dead fish in there overnight to find them gone in the morning. its in a ten gallon tank (too small) and is about 6 inches including the pincers.
bluecrayfish.com has a pic of a white in it's gallery. Beauty! I'm about to set up a larger tank for some new blues I have coming in. I'm wavering between a 29g and a 55g. Bigger is better, and in this case only about $30 more, but the space man, the space...