jetajockey said:I'm not sure if I understand the question completely. I have planted tanks that could read 0 nitrates but they get kno3 dosing regularly to avoid it from happening.
jetajockey said:Are you using any sort of chemical filtration?
Plants can reduce nitrates if they are densely planted/lighted well enough.
One other possible concern is that with a blackwater tank, the pH can drop down into the 6's which significantly slows down the nitrification process, if it gets low enough it can stop it all together, so you wouldn't see any nitrates then either, but you would see some ammonia buildup.
jetajockey said:well the plants can utilize ammonia also, so that's not out of the question either. I've never really done extensive testing on acidic water so I can't say for sure, but I do put some alder cones in some of my tanks from time to time to induce breeding.