My friend's betta has had a persistent case of fin rot. After so much time and research, none of the causes of fin rot are present in her tank. Her water parameters are 100% fine, and the betta is not stressed in any way whatsoever. The two neon tetras and one whitecloud dont bother it and they are also perfectly healthy. The betta's behavior is perfectly normal and it is very active. We have tried:
Salt in aquarium
Nothing is working. Sometimes his fins will get better for 2 or 3 days, but then just gets worse afterward.
What should we do? We're running out of options.
She does a 25% water change every week using seachem prime for her conditioner.
10 gallon tank.