Took over a 18p gallon tank after my buddy killed everything on acciendent. He is moving and doesn't have room for tank. I kept the rock. Changed the sand. Anyways. I've been noticing these tube worms and was making sure they are okay. I've done a little research but cant find pics of these! Are these good to have? they are all on the rocks. dont see any in the sand. Never owned a salt water tank but I've always loved them so new to the hobby. Active scuba diver! Please help!