That should be the previous thread.
I had thought it was fin rot, someone else suggested it may be fin melt.
He started getting fin rot 2 months ago, I got a water testing kit and some AQ which I used for a month but it just got worse, so I reached out here for help. He's in a 2 gal tank (When I first got my two fish I was told to get a tank between 1 gal and 5 but I've read on here tanks should be 5 to 10 gallons).
For two weeks now I've used triple sulfa on him and he's been improving, he's less lethargic and eats more. After one week of triple sulfa I stopped and he immediately got worse. He was lethargic and just resting on the bottom of his tank. I turned off the filter and started another week of triple sulfa. His appetite immediately returned and he was swimming around again. I have 3 more doses in the pack I have, not sure if I should buy more TS or something else. Suggestions?