For the past couple of weeks I have been plagued with Green Dust Algae on my 75g and 55g in the basement. I had assumed it was a CO2 issue since I have been dosing daily with 2ppm of KNO3 and 0.2ppm of KH2PO4. I have probably forgotten a day or two along the way but have been pretty consistent. I would clean the glass and put the diatom filter on the tank but the GDA would show up again within a day or two of the diatom filter's removal.
Since I received my LaMotte refills last week, I decided to test for NO3 and PO4 today. Both the 55g and the 75g were at zero ppm of NO3 and zero ppm of PO4! It seems that low ferts was the cause of the GDA and not low CO2. While neither of these two tanks has BBA, the 75g has a diatom algae bloom going on also.
A lot of folks say that either low or high NO3 levels can contribute to GDA and this may be a little bit of proof that low ferts does indeed cause some algae
Neither tank had much Green Spot on the glass but I upped the PO4 anyways.
I just thought everyone might like to know