My Clown loaches are curently all about 3-4".. and all of them live inside a big bit of bogwood. When ever I clean the tank, I take this out, they are always still inside. On occasion, they wriggle out while the bogwood is still out of the tank, and I've had to scoop them up and dunk them back into the tank. At this point, I have been bitten a number of times, just a little nibble, but potentially painful.