Cyano? Help please.

[carriej]

Seem to have heard and tried a lot of different "methods" but none seem to work. I have starved it, vacuumed it, used more flow, removed it, skimmed heavily, cut back on all foods, more water changes... I can't kill it. I remove it, go check on the tank... Looks spotless. Wake up in the morning, coated again.

How does one keep a sandbed clean? I was under the impression that they should not really be touched or disturbed... It's a 150 gallon system and I only have 7 fish. 6 small ones (two clowns, gramma, goby, pink fairy wrasse, lone chromis) and one medium ish fish a small scopas tang. So it's not a huge bioload... I don't know what gives.