I know I have atleast two gorilla crabs in my 29G biocube. They are the size of a dime or a little bigger. Ive tried crab traps and never been able to get them out. Ive even tried hunting for them at night, but they are very crafty to say the least. Ive had the tank set up since march of this year. How concerned should I be about this? Ive never seen them eat anything. I had an anemone die recently and a shrimp die once and I only saw hermits, my mithrax and emerald crab munching on them before I removed them.