Freshwater crabs in my tank

Question

Will they harm bottom dwelling fish and plants with their claws, i want one but im worried i have been told yes and no.

Could i tie the pincers together with rubber bands to stop them killing stuff?

Answer 1

Depends on how small the dwelling fish are.

Answer 2

I have one or two cray fish in my tank all I do is take the pinchers off once a week or when I full clean my tank every other week.