Well, tested PO4 yesterday and it was at .2 ppm. This is double what I've been measuring lately, but I didn't do a water change last Friday, so that might be why. Either way, dosing NO3 isn't working as well as I hoped. I could try increasing the amount of NO3, but what I really want is to just drop PO4 to a level where it can naturally be consumed by the tank. I did a bunch of research into lanthanum chloride. Seems I only need a small amount to drop my PO4 to undetectable levels. Going to try this route. So frustrating since for over a year, everything was balanced and fine. Then one equipment issue upsets everything.