Hi Matt.
I find a reasonable Kh is 6. It stabilises Ph without raising it too high. Raising Kh further will drive Ph higher. As an aside, I keep Gh at about 6 as well. These figures seem to suit my tetra/Cory/RCS tank. Other fish may prefer a higher Gh.
I think there might be a conception that all the ammonia is converted to nitrite, giving a high nitrite reading, and then converted to nitrate. In reality the ammonia is slowly converted to nitrite and the the nitrite subsequently converted to nitrate in a continuous cycle. Therefore the nitrite reading is likely to be low or undetectable. It seems rare that keepers have problems specifically with excessive nitrites (I might be mistaken). Because ammonia is added to a certain ppm it is easy to read. The final stage of nitrates are also easy to measure because they remain until diluted by WCs or plant absorption. Nitrites are part of the ongoing process from ammonia to nitrates and are often very low apart from in the very early stages of starting to cycle your tank, when only the ammonia/nitrite bacteria are in abundance and the nitrite/nitrate bacterial have yet to colonise. If you have used a piece of seeded media from another tank to seed your filter then the chances are that both bacteria are already present and nitrites will not have an obvious spike.
Sent from my iPhone using Aquarium Advice