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.