Merk, thats exactly what the crabs and snails are doing....they are waiting to form a pack and then attack the coral! It really was weird to watch. As soon as I added the crabs, within minutes they were all over the coral. It was kinda spooky the way they formed a pack and waited for each other to attack. It also looks like part of the tube on my featherduster is eaten away ( part of the worm is sticking out of the bottom). I am going to put some of the crabs in their own little tank, what do I feed them as there is no algae in that tank yet? The hermit crab food I saw at the pet store all said for land crabs, what about marine crabs? Will algae sheets work?