i believe once it is mature it can be moved, as a juvenile it is attached... if its still attached id just move the rock if thats possible, if not then just wait it out unless the BTA is actively stinging it, it looks pretty happy where it is in your pics. mine is about 3 inches wide and ive had it for probably a close to a year and its mature and i move it easily when i clean my tank. i was told they like the sandy bottom but mine seems to prefer the racks or up off the bottom because my hermits/conchs bother it constantly on the bottom