I have two BTA's and thought I had out-smarted them by purchasing the rock they were attached to so they would stay where I placed the rocks. That worked for about a month and then the one on the right side of the tank went for a stroll. The Zoas were less than impressed as he walked over the top of them and his new mushroom neighbors think the neighborhood is going downhill but he seems happy. The other one was doing great staying roughly where I put the rock but then he moved into the rock behind him and yesterday he split, not meaning to leave, but rather to become two. One of them claimed the back of the rock and the other the front. Fun to check on them through out the day to see the changes. The surrounding mushrooms don' care for them at all but they can move if they want to.