once I do the 50% water change in I good to add fish at that point?or wait to see if I have nitrates that go up again a few days after thatI would suspect your 80ppm readings are mite accurate than the previous 5ppm readings you've been posting. If your done ghost feeding and dosing ammonia, then you could do a 50-75% water change, otherwise I'd wait. I use the salifert nitrate treat kit and my reasons seem to always ne consistent.