One day I looked closer at him seeing him not as energetic as he usually was and noticed his entire top fin (not sure what it's called) was gone. He is a very dark color so it is hard to even tell it is missing. So assuming he had fin rot, I quickly put in betta revive because people seem to swear by it but...it has been a week and he hasn't gotten better. Actually worse...I really want to save him if I can but I'm not sure what else to use. I've heard the "cure alls" at Petsmart etc aren't very good and I need something stronger. Does someone have any suggestions? I tried to do research but all the forums I found suggested things that aren't available anymore. I'd prefer to start his treatment today if there's something I can get at Petsmart. Any help would be appreciated. For reference he is in a small 1 gallon without any gravel or filter because it is my "treatment" tank. I've been changing the water every day but no notable difference.