i'd recommend red slime remover as a TOTAL LAST resort.
first, you really need to figure out WHY you have it. not enough water movement, too much phosphates and nitrates, over feeding, lights are too old or run too long, etc.
to kill it off, if you don't have corals, turn off your lights for 2-3 days. your fish won't mind. cut back on feeding, check your foods for phosphates, etc. figure out how to prevent it, and you won't get it. suck it off your sand with your water changes. if you do all this THEN go ahead and use it. It worked like a charm for me, but ONLY after i did all these things.