I can't tell either. At first I thought it was a baby snail bc I have quite a few of them in the tank. But after keeping an eye on it, the coral doesn't seem to react to it much. I have an acro crab in one of my acros and it's doing fine. I'm just going to keep an eye on it. Hopefully I'm not making a mistake and waiting for it to lay eggs.I can't tell - snail or crab?