One of my gold guppies (F) in my daughter's tank died tonight (or yesterday? I noticed this morning). Body wasn't chewed up so I think it was rather recent.
I proceeded to check the water and I got PH 7.8, Ammonia 0, Nitrite 0, Nitrate 80ppm (ouch), TDS 400ppm.
Tank is a 15G fluval flex. A...