Need help quick! I posted in the fish disease forum that I just lost a honey gourami... it developed huge lumps and died within 48 hours. I had tested and done a water change a few days earlier and all was fine. I did a 25% change yesterday again. Today one of my glofish is dying. No lumps, but is gasping on the bottom right now. I just retested and all parameters are good EXCEPT nitrates are 0 according to API! they're normally about 20. The only thing I can think of that's different is that I put 1/3 of a mesh bag of PhosGuard into the filter about a week ago. Would that kill the nitrates?? I'm heartbroken and very worried about losing the rest of my fish. What should I do?