Ya, I remember someone telling him not to take out the rock after alot of us told him it would be better. He was worried about messing with the cycle of the tank after that. Moving the rock can cause alot of crap that is in the rock to come out and be in the water, making the water levels change, but will not hurt enough to matter. You could do a 30% water change after taking to rocks out in order to get all the crap floating around out. That would make a big difference. Just make sure your filter stays running and you will be fine.. Make since to anyone...lol
I would wait on the sand, but it is alot better than the rock you have in there. Bare bottom will be better for him rt now. Easier to keep clean and easier for him to find food. I would still also seperate him from the other tankmates. That way all the food you put in there is not being eaten by everyone else and he has a chance to get some as well.
glad he is better. I figured that is what his disc would do when starting to heal. Id never seen a burn like that happen, but have seen some rays with good bite marks and they heal the same way...
keep up the work and he will get better....