Conversely if you let the plants deal with the ammonia you will never get nitrites or nitrates. I used to be an adherant to the theory that there is no such thing as too much filtration. The last few years i have gone completely the other way. They tank in my signature picture is 55G and overstocked. The filtration on the tank is adequate (but not good) for a 20G tank, even if we ignore the fact that my water is acidic so what bacteria there is is not very effective. My nitrates never reach 5ppm (even when I went on a 3 week holiday). No detectable ammonia (ammonium in my case) or nitrite.
FWIW I have never vacuumed the substrate. About 8 months ago I replaced my 5 year old substrate because I wanted to change the colour. I did this without removing the fish (not a practice I recommend BTW). Turns out there weren't enough pathogens lurking in the sand to affect my fish. All of the glowlights and about half of the cardinals in the tank are over 6 years old - these are fish that are sensitive to poor water quality
