I have a Betta that's getting sicker and sicker and I can't figure out what to do. When I first got him around February, he was perfectly healthy. Sometime between then and now (say 3 months ago) my mom noticed his tail was starting to shrink. I looked into what it could be and fin rot is the closest thing I see to it. All his fins are shrinking and now it's so bad he has almost no tail and top fin.
He was in a cycled ten gallon with another Betta and a couple shrimp and I moved him to a three gallon quarantine tank and treated him with Bettafix two times but to no avail. The fins are still disintegrating.
What are some other things I can try and could it be something other than fin rot? He's not looking good at all; he can't swim and I feel like he's feeling ready to die soon.
Keep in mind I just moved and don't have that much money right now.