Mouth-Brooder-Fanatic
Aquarium Advice Addict
if u want a crab, what about lowering the water level to half way and putting a mini upturned plastic basket (with loads of holes) so it stickes out an inch above the water but is weighted to the substrate? then they can climb out, breathe, find food on the substrate (whatever you wish to feed them) and u can have fish. i had fish with mine, they never got eaten. but i always left food around for it.