I have a moderately planted ten gallon tank with paintball CO2. My nitrites seemed to fluctuate and my fish didn't seems to happy. I purchased a air pump and small air stone. I have it on a timer and it goes off and on several time through out the day. My fish have never been happier and my plants are doing great even though I sometime have the CO2 and air on at the same time. I don't know if it's the air pump or not but my nitrites seemed to drop to zero as well.