What species of crayfish is it. I am suprised it is not gobbled up. I have been thinking of a scavenging crayfish to put in with my fish but i am still fighting weather to do it or not. Because i wrong move the fish are eaten. Or the crayfish is eaten when it molts.
*EDIT*
By the way i am glad the quartz is working out for you.
*EDIT*
By the way i am glad the quartz is working out for you.