I just did a 20% water change Saturday and this brown hairy algae is all over my sand bed again. I used CaribSea live sand for my sand bed and it says no silica. My RoDi water that I did the change with started at 0 conductivity. I have to think that I have silica in the tank from the sand. Has anybody else had this happen to them with this sand. Will it go away on its own eventually. Is there a way to reduce silica in the tank? I have come the conclusion it is NOT hair algae but diatoms.