My comet Pico has been having these issues on and off for a month now. He will be fine at dinner, and then at bed time he has red streaks on his fins and red patches on his body. I started treating it at first with melafix and frequent pwc but it kept getting worse(more, larger patches and localized swelling). I used API fin and body cure assuming it was septicemia and that seemed to work. It came back a week later and I did a water change and then dosed the tank with the last dose of fin and body cure I had and it worked but once again, about a week later, Pico is once again in a bad way. He has been active and alert and has not had any appetite issues, even when he was worse than this. Red marks seem to consistently be on the same side. I have been watching the water specs ever since this started and they have been fine for weeks. Water quality seemed to be fine when the problem first started too. I am in Canada so several API medications are unavailable PWC: 25% weekly Aquarium has been going for 1.5 years Tank: 20 Gal Tankmates? No PH: 7 Nitrates:0 Nitrites:0 Ammonia: 0 Temp: 18C Plants: several Java ferns - I added 3 very tall ferns right before this started, but the other shorter ones have been there since I started the aquarium. Does anyone have any suggestions on how to help him?