This situation actually also happened to me. I did not have a nitrate test kit and my tank is a bit overstocked. I, however, am doing 25% weekly water changes but apparently it was not enough to reduce the nitrate levels. Also it has only been about a month since I doubled the fish load.
The first time I measured my nitrates (the first time I did it I did not shake the bottle reagent #2 for the Aqua Pharm test) correctly it was VERY red. Probably > 160 ppm. Since then I did 4 daily 50% water changes and so far the nitrate has stabilized to 10 ppm (planted tank).
The article was REALLY helpful. Thanks RTR.
IceH2O: Are you using the Aquatic Pharmaceuticals test kit? I am asking because it seems hard to distinguish the levels from 40 upward. It doesn't actually matter since it is not advisable to get to levels that high. I am compiling info for a test kit database/FAQ (in the products section) so any info is appreciated.
