I'm starting to believe that other filters will stop this working.Well can't hurt to buy one and try i guess. It's kinda expensive though. Even though the manufacturers claim that you don't need any other filtration, i plan to run this as an addon to my external filters.
The reason there are no nitrates is because of the single conversion from NH3 or NH4 to H2O +N2 is the reason there are no nitrates.
I can't find a chemical reaction that uses hydroxil + nitrate or nitrite.
I believe that if you put this in at your only biological filter, and use everything else as mechanical, that's how you get this working.
I don't believe that this does anything to nitrates or nitrite, I think that it neutralizes ammonia in a single step rather than ammonia->nitrite->nitrate...
But rather NH3 or NH4 -> H2O + N2