So I just started a new tank from being out of the hobby for several years. I started a 12g nano. it has been up and running for a couple of weeks now and i just noticed a crab like invert inside one of my pieces of live rock. I can only see very little of it. It has very small claws and several legs. I think I can see white on the front of it and it looks like the rest is brown. I know this is not very descriptive and I am waiting for it to come out so I can get a pic. Any thought?