I wouldnt quite go that far. ya they can move and they can move fast when they really want to. I have 2 RBTA's, they stay put. once and awhile they will move a little, if I modify the powerheads or something. Mine are very large though(8" or so in dia), the bigger they are it seems the less they move. When I first got them i literaly watched the larger crawl close to 2 feet, I was amazed at how fast it did it too. All its doing is trying to find a happy place, once it does, it wont move unless it has to, or you change something.
how big is your bta? where is it in your tank(height from the top)? what kind of lighting do you have? do you feed it?