Whats the best bottom feeder for a reef tank?

I have a 54 gal tank with 3 turbo snails, 4 hermit , 1 clown, 1 coral beauty, 1 dotty back, 1 brain coral, 1 elegance coral, 1 arrow head crab, and pink hatian anemone. I feed the fish every other day and the corals once a week. The rocks and gl stay very clean but the sand turns nasty very quickly any suggestions on what i could get to help with keeping the sand clean. I was going to get a cuber but was told they release a toxin that could kill everthing else.