I had 3 blue crayfish but only have 2 now. One has grown quite big, the other is growing and the 3rd didnt seem to grow. I think the other two ate the little one. It didnt grow as it only had one claw when I got it and put all its energy into growing a new one, which stunts its growth. Pity, I liked it. Still, the other two are doing well. I had them in a small tank at first as they were only babies and decided to upgrade their tank to a bigger one. First pic is of them in a buddha themed tank. They are now in a lerge tank with sand.