the tank is 125 liters, he has 4 other gold fish and 1 pleco as tankmates and their alll fine, temp is around 27 c. ph. is 6.8, kh mg/l is 180, gh mg/l is 500, nitrate no3 mg/l is 10, nitrate no 2 mg/l is 0. those readings are using king British test kit I hope that helps I am totally a new...