It will go away if your nutrient levels are low. I don't get debris on my rock. I have adequate flow in the tank to limit this. Power heads serve 2 purposes: One is to provide corals with adequate flow, and the other is to keep the tank healthy by keeping detritus (uneaten fish food and poop) suspended in the water column long enough for your filtration to remove it.
The rock in the pictures on your other thread came from a nutrient rich environment. You've got to correct that or you'll always have algae problems, snails, crabs, and urchins, or not.