I was bragging about the 30 gal tank that cycled and all fish survived. I spoke too soon, they came down with ick. I bought Nox-ich with malachite green, treated tank at half strength 5 days now(because bottle said use half stength if plecostomus in tank). Tonight I found 2 dead fish that were both active and eating this morning. 1 is white skirt tetra, other neon tetra. I just checked and got ammonia at 0 ppm, nitrite 0, nitrate 20, pH 8.8? I don't understand the 0 ammonia because there is no carbon in filter past 5 days. pH is usually 8.2. Any ideas?