brown macro algae

175g reef with 60g sump About 125-135lbs LR 1-2" sand bed Temp stable at 78-79 PH at 7.8 (working on O2 issues) Ca at 440 Alk at 10.4 (see PH and O2 issues) Mg-1295 Nitrate, Nitrate, Ammonia, Phosphates all showing zeros No algae issues in the tank (corraline is good) Tunze protein skimmer...