When I ordered from aquariumfertilizer.com I bought some mono potassium phosphate too, but it was so long ago, I couldn't remember why. I need to review the estimative index system I guess. My phosphates have tested really high all along, a phosphate remover resin brought them down to reasonable levels, but once removed, they returned in time. But after dosing only potassium nitrate in the tank, a week later showed lowered phosphate levels, so in time it may be necessary to add it to the mix. Can I just add it to my PMDD mix? I was using Excel primarily because of its off-label algae fighting properties, the tank has CO2 injection. I was having trouble with brown algae and more recently BGA/cyanobacteria, particularly on top of my driftwood which I read could be a sign of a nitrogen deficiency as near the surface it can get nitrogen from the air. Except for a new leaf on an anubia that looks particularly healthy, I haven't seen any signs of improvement yet, but the BGA I vacuumed out hasn't returned and nothing looks worse off so I'm keeping my fingers crossed.

Michael