[organism]

If your phosphates are 0 and your nitrates are 0 then you need to feed more to raise both a bit. You're probably running too much GFO since it shouldn't be that low imo. Usually tanks that are limited by nitrates will have higher phosphates since once nitrates are gone the bacteria stop breaking down phosphates. Dosing nitrates could help though.

The stump killer stuff had a smell and messed up my goni, but I've heard of other people having good results. I got reagent grade potassium nitrate on Etsy and it works great. Mixed 250g into 1L of RO water, and to find the dosage for my 75 I dosed 3ml, waited 20 minutes then tested nitrates. I think 10mL will raise the nitrates by 5ppm in my tank or something along those lines. Kept it going until nitrates were at around 10. Now I dose 3ml once a week to keep them between 5-10.