I two had a diatom problem a couple of weeks ago, I took an old powerhead and "blasted" off my rock, blew the sand around and did a 25% water change added 2 Powerheads and I added 5 Mexican Turbos, 4 Nass, 1 astrea, and 1 conch (i didn't have much of a clean up crew just 2 blue legged hermits and 1 scarlet hermit) 2 days w/o lights and I have noticed a major decrease in the amount of diatoms I have.