Hey guys I need some help IDing something. There are these 3 things in the tank that we don't know what they are. They are all the same but different sizes. They have 2 spouts, one bigger then the other. The spouts have little hair like thing on the openings. I would take a picture but they only come out at night and when I use a flashlight they retract into there holes. At first I thought they were some kind of clam but I'm not sure. The first one I saw is in a clam shell that is encrusted in the rock so I guess it was a clam but the others I found last night are not in shells. Do these sound familiar to anyone?

