I have gotten rid of unwanted pests on my live rock by putting them in a bath of low salinity water like 1.010 in a tub with a power head and change the water every day for three or four days until they are dead then wash the rocks off with fresh water. Then I put them back into fresh salt water at full salinity for a few days then put them back in the tank. It kills everything but the coralline Algae and rocks look normal again. Not sure what to do with sand. Not sure you could treat the whole tank that way because after the first day the water is pretty nasty. I think I would consider starting over. Sorry.