tug

Correct, for me, 11ppm 3x week is probably a little much truthfully. I dose closer to 6.5ppm every other day. I look at the plants uptake of NO3 and after throwing in a weekly water change of 60 - 50% IME the tank resets closer to 10ppm.

I was only pointing out lildark's dose amount seamed lean, but as Philosophos points out, fine for a low tech tank. This important variable (low tech -vs- high tech) as well as plant mass is what I was missing from his calculation. Without knowing more about lildark's situation I was only trying to ferret out the process. Which it seams to have done for me anyway. For lildark, not so much. Does the tank have high levels of light? Is it CO2 enriched with lots of plants? When I first started doing this I would get away without adding much, if any NPK. CO2 was so limited and my substrate was/is such crap (only flourite and gravel) I spent most of my efforts on improving the amount of CO2. Now that I believe levels of CO2 are non limiting I have time to tweak the EI formula and think about replacing the substrate.