Originally Posted by
2wheelsx2
One thing you can do is ensure that your kit is reading properly. Do a reading before the water change and then after the water change. If you are at 20 ppm before the water change and you do a 60% water change, immediately after the water change, you should be at 8 ppm. If not, there is something wrong with you kit (probably your kit can't be that accurate and will show 10, but that should be close enough). And then if you take a reading the next day see if it's again at 20. If so, you're gaining 12 ppm a day, which doesn't sound reasonable to me for just 6 x 4" fish in a 55 gallon unless there is tons of leftover food in the tank.