I have not keepted up on one of my tanks like i should have been on water quality. I wanted to add a new fish that is very tempermental on water quality. I tested the water and found amonia was up but not bad, ph was higher then required for the feature new inhabitant, nitriteswere ok but the nitrates was off the chart. the current fish showed no effects from the nitrates so i did a 50% water change this morning. After letting the tank run with fresh water i retested the water and the nitrated are still at the top of the chart but it took a few minutes to get there instead of almost insantly like this morning. Is it to soon for another water change are would it be ok to do another 50% change?