Salt is 1.026, temp 78, alk 6.5, ammonia 0, nitrite 0, nitrate 5-10, ph unknown - below 7. Yesterday I ordered seachem ph buffer. It just arrived. I've been told yes use it now and absolutely not, so IDK. There is no issue with air quality. The aquarium isn't far from the patio door that's almost always open. Hvac guy was here last week and everything tested normal. The tail fin of the fish now looks like it's fraying, but it could be from it hiding in the rocks all the time. It's been swimming a bit more than laying on it's side. I was close to euthanizing it, but I'll wait to see what you guys say. Another forum told me it has uronema or brook. What I don't understand is why the only fish not affected are clowns.