Keep everything at < 0ppm (less then) once cycle takes place you should never see ammo or nitrites rise unless something is decaying or something is wrong. Pending on what kinda tank you have will determin what level is acceptable for your nitrates. I have seen
FO systems with as high as 50 ppms (don't recommend this)
FOWLR could be a bit lower and of course with a reef you would want to keep it as low as possible, closer to 0ppm the better! Lol
Hope this helps
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