I had one tha became two, then at one point 8. Never lost a single coral to them (except a punk Hydnophora frag). My mothes only roamed after the split, but usually to a spot under the rock, then back to within a few inches of where they were before the split. The babies roamed for a while, but didn't seem very aggressive while on the move. They would walk over SPS colonies with only minimal signs that they had done so. Mine were all GBTA's, but I've had an RBTA that roamed a bit more (not in an SPS tank), but it never hurt my acans. They love to give themselves buzz cuts, though. Any ph within reach is a candidate. I only ever lost one due to extended buzz cuts (the RBTA-didn't get to it in time to let it pull itself out of the mesh).