I agree with the theory of EI, but am just suggesting that every source water and every tank is different. My water is high in PO4 and my plants (when happy) are Nitrate sponges.
I was using a 2:1 rather than a 4:1 NO3:PO4 ratio with my fert. As such I was dosing 4.4 ppm 3 times a week. By dosing 13.2 ppm a week, with EI, I should of maxed at 26ppm (assuming no absorption). Testing indicated that I peeked at 30-40 ppm PO4. The difference between my measured ammount and that is probably attributed to doing slightly less than a 50% change (40% change would have maxed me at 2.5 the weekly dose - roughly 33ppm), plus my water having 1-2 ppm. Perhaps my bioload is also contribituing to my PO4 levels.
Testing several times throughout the week has shown me that my PO4 has not dropped below 1 ppm (perhaps due to bioload? Phosphates in the fish food?). Meanwhile, I have increased my dosing from 9 ppm 3x weekly to 12ppm 3x weekly and am still not having more than 10ppm right before my water change (which is about 36 hrs from my last macro dosing).
Today is water change day, I will test PO4 and NO3 again tonight to see what my end of week levels are at-My observations above were after 4 weeks of this testing. I removed a lot of my fastest growing stems last week, so absorption may be down.
Testing showed a that PO4 was a little low (.5ppm rather than 1ppm), while NO3 was resting at 10ppm.
58 gallon oceanic, Kessel 360 tun sun, pressurized co2, eheim pimp #179 - 2217 and diffuser
Last edited by jgc; 01-18-2006 at 11:38 AM.