If ammonia went down and nitrite shot up, it's stage 2 of the filter cycling process.
Stage one is where you add ammonia and the first group of bacteria develop and eat the ammonia and convert it into nitrite.
Stage two is where the next group of bacteria develop and start eating the nitrite and convert it into nitrate. It will be a couple of weeks before this happens.
The best way to reduce the levels is with 75% daily water changes and gravel cleaning the substrate. Do this any day you have an ammonia or nitrite reading above 0ppm (if there's fish in the tank).
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Stage one is where you add ammonia and the first group of bacteria develop and eat the ammonia and convert it into nitrite.
Stage two is where the next group of bacteria develop and start eating the nitrite and convert it into nitrate. It will be a couple of weeks before this happens.
The best way to reduce the levels is with 75% daily water changes and gravel cleaning the substrate. Do this any day you have an ammonia or nitrite reading above 0ppm (if there's fish in the tank).
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.