Specs: 75 gallons. Sump 20 gallons. Two compartments that are fuges. Both have chaeto, about 2 lbs LR and RECENTLY added DSB. Im thinking maybe this is the source? The tank could be going through a mini-cycle?? Other fuge is a 2.5 gal CPR hang on with chaeto only. Coralife 125 Superskimmer - works pretty well. Phosban reactor w. phosban that needs to be replaced. Mag 9.5 return. Main tank. Shallow sand bed. Around 100-110 lbs LR. Stocking - 2 2inch Heniochus Diphreutes. 2 2 inch Ocellaris Clowns. one 3 inch royal gramma. One mandarin drag doing very well. Inverts: mated pair of lystmata cleaners. 1 8-10 inch tiger tail cuke. About 10 turbo snails and one giant mexican turbo snail around 4 inches. Corals: LPS - Frogspawn, candy cane, acan. Zoas. Looking to pickup mushrooms, zoas, and lps at swap sunday. Salt is Tropic Marin Pro - Reef. Water change is around 5 gallons a week. Source water was RO from an LFS that i think had shady water that i never tested. I am now getting an RO unit that will be more dependable. Im thinking that the shady RO coupled with the sump DSB cycling could have raised the nitrates and phosphates enough to cause this algae outbreak. The algae seems to be diatom covering the sand. There is some hair algae on rocks but nothing bad. Some red algae is even starting to cover the acan - not good! Zoas seem to be unharmed but probably arent growing as much. Im thinking i should just do a bunch of water changes, change the phosban and wait till i get the RO unit which will have much better water. Any other suggestions?