Thread: fin rot on my beta?

my beta's dorsal fin started turning white last week and now it is completely white. he still eats and moves about his tank so he doesn't seem sick but i don't know why his fin is white. could this be fin rot?

Definitely. I'd remove any activated carbon from the filter and begin treating with any of the many antibiotics available. Maracyn TC, Maracyn + Maracyn 2, Furan 2, Triple Sulfa, Trisulfa, Kanacyn, or any of the similar medications are ideal.