Hi All, thanks for the help in advance.
Tank size: 60L / 15.5G
pH: 7.5
ammonia: 0
nitrite: 0
nitrate: 0
kH: ?
gH: ?
tank temp: 24
Fish Symptoms (include full description including lesion, color, location, fish behavior): Most are lethargic, are not swimming around, they just stay up there, ...