Examine your rock work, make sure that there are places for him to put his pedal disk into BTA's love to hide their foot in such crevasses. Give him a full week at least and see if he stays there before attempting to move him, or the rock work. Examine the water flow that he is in, it could be one reason that he chose this location, but he could still be resting up for another move, let him decide for now.
I'm really glad to hear he is doing better, give him a full week before trying to move him or the rocks, try to figure out why he likes it there. You may even want to move your power heads a few inches in some direction which will change the pattern of the current inducing him to move.
Thomas