I have 1 betta in a 5 gallon, heated, cycled aquarium. Silk plants only, with a little bit of gravel. One of the plants is very tall and slows down the current quite a bit.
About three weeks ago, I notices a part of his dorsal fin looked a little torn and black. The next day his fins were severely torn and eroded. I watch him quite a lot, and I've never seen him nip at his fins. He did seem a bit agitated though.
All signs pointed to fin rot, so I took him out of the aquarium and put him in a 1 gallon, heated, unfiltered hospital tank. I treated him with aquarium salt and daily 100% water changes for 5 days. After I ran out of aquarium salt, I kept him in his hospital tank for another 5 days, changing the water 100% every day. His fins stopped rotting away and they looked way better. He ate regularly and swam and seemed better.
I totally cleaned out his 5 gallon aquarium, all the plants and got totally new gravel. I moved him back home the day before yesterday. I looked at his fins today, and they seem moderately rotted and torn up again. I'm getting extremely frustrated after having spent many hours treating and changing water. I don't really know what else to do. I never see him nip at his fins. There is nothing sharp whatsoever in his aquarium. Any advice?