I have a 10 gal. QT tank running with a Marineland Penguin 100 power filter and currently have a Coral Beauty Angelfish in it. He has come down with a case of body fungus which I am treating with PIMAFIX by API. My problem is that I have discovered the Nitrate levels in the tank are now around 80 ppm...I have done one water change of about 15% and still no overall effective change in the Nitrate levels have taken place. My ammonia levels are at zero, and the excess Nitrate is now messing with my pH levels. Since I am medicating my fish, I am wondering if it is safe to do another, more complete water change to lower the Nitrate levels in the tank? Also the PIMAFIX has instructed me to remove the carbon filtration on my filter, is this affecting Nitrate levels as well? Thanks for the help.