Gustauf

Thanks for the input. Tank has 2 airstones already. Looks like it's time to set up the quarantine tank and get some aquarium salt. Any ideas what would be causing the gray patch on his side?

Relatively new fish keeper here. My betta of about 18 months has been becoming listless and developing discoloration that I can't identify. Ph 8.1 Nitrate 25 Nitrite and ammonia 0 Gh 75 Kh 120 Temp 78-79 All parameters have been stable, test weekly, water changes sporadic. It's my wife's tank, and she tends to clean it couple times a month with about 50% water change. Only tank mates are two RCS and two amanos. Recent history, case of fin rot that got farther along then it should have, treated with 2 rounds of single dose ich-x and maracyn with good result for fin growth. A while later full treatment with maracyn for lethargy and the discoloratons near his tail, lethargy resolved, but discoloration was unchanged. Later 5 days of ich-x with no significant change. Now spots seem to be increasing in size and number, and dark bands have developed behind the gills. I just feel like I'm missing something. Any idea what might be wrong or other empirical treatment options. Or am I just over-worried about a fish that is getting lazy? P.S planted tank with a moderate algae overgrowth only treated with mechanical removal.