What type of lighting do you have? I have a LTA that was under power compacts and it took 3 months for it to plant itself in the sand. It drifted from the front to the back and then came back to the front. I moved it to my new setup with halide lighting and it planted immediately and hasn't moved since. It hosts two black saddle clowns that are pretty rowdy. Also how large in diameter? A small LTA trying to host two clowns could be really stressing it out like others have posted. If it is hiding under the rock work and trying to extend underneath where the clowns can't get to it then it sounds like the clowns could be the primary stressor here. Can you move the clowns to another tank for a few days or a week to let it have time to adjust to the new conditions?