mantis shrimp?
 

i have found one in my tank, now he must have been there for a while and is not attacking anything,i have a few hermits and fish,lta,monti cap. he just hides in his hole in the rock and when i feed the fish he pokes his head out and grabs what he can. are there less agressive mantis shrimp? or should i try and trap him and get him out of there?

thanks,kristian

As he gets larger and more hungry he will get more agressive. You will start noticing empty snail shells around. I have had one in my tank for years, it kills what it can but I have no way of getting him out so i just buy more snails.