My current tank is about 3 years old not and I starting having a red slime algae (diatoms) on sand and now some rocks and coral. I'm at a total loss any suggestions would be good. All new filters and membrane on RODI, levels are good. No Nitrate or phosphate (at least the read zero like normal). No other algae issues. The weird part is if I turn the lights off for a day it actually gets a lot worse. This goes against anything I've even experienced. Skimmer is working great and over sized for the tank, sump is clean, socks changed every two days and nothing has changed in the tank. Even added more flow when i had plenty already.