Thanks problemman. I'll try that with the nitrates. Does that mean I should lower phosphate levels accordingly?
I trim the HC weekly (people think I'm crazy), but after a couple weeks of that, it sort of learns to grow and stay that low. Especially when it's well rooted, it stays nice and short. Biggest problem I've seen with HC is that if you don't trim it, you eventually get the toupet effect where it uproots and just sort of sits on the substrate.