not sure what you are dosing, but it sounds like you are putting in something keep ammonia down because of your sand bed switch? what are your levels at now , after the substrate switch? i wouldnt add anything you cant test for.
i saw that it is on a frag of rock, but why did you not put that frag wedged into your LR? this way the coral can spread and climb onto your LR. it will have a tough time growing with nowhere to go, and rolling around,.