to bad cray claws and cat claws/finger nails are nothing alike....
..it would be more akin to chopping off the tip of your finger(or your cats toes,,,just the tips) every few months..but its OK because it will grow back.
to the OP: i have just started keeping crays..they are fun little things^_^ but from what i have researched you try them in your tank to see if your cray will eat your fish , and run the risk of losing some fish you like. or you get there own little tank.
I have a marbled cray, she is in a 2.5 for now with a few guppy fry..that she ignores...snails on the other hand are her favorite! she destroys them...like 10 pea size ramshorns and pond snails a day....little monster^_^ good thing i have s surplus of snails.
I found most of it depends on the individual cray....and the species.