Do you have any before pics.....it doesn't look too bad and I don't really see any rot....that usually will look somewhat crusty and discolored.....
Sometimes the long fin males can have fin issues due to the filter/water movement as well as space...some...not all....these abnormally long delicate fins can get really tattered with use from swimming and the water movement....kinda like a flag in the wind effect.......
You may need to turn off the filter and add some IAL or dried Oak leaf to get him healed up and fins toughened up some.....sometimes the tannins will help toughen fins and scale.....
Since you caught this early-he may not need a salt treatment for now-but I would increase the water changes to 50% twice weekly for a couple of weeks-along with removing the filter, adding a tannin source and increase nutrition by adding another food to what you are already feeding-good quality varied diet fed in small frequent meals.....if you have access to live mosquito larva-offer a few rinsed for one meal a day to boost protein and you can even roll the pellets in fresh crushed garlic juice too.
How many and what species of live plants do you have....
It can sometimes take weeks to month to get full re-growth/healing and sadly if it is partly related to water movement and/or space-it may be a long term issue and all you can do is prevent secondary infections
Here is some info that may help you understand more
http://www.bettafish.com/showthread.php?t=78317
Lovely fella....nice find....it is sad sometimes when the fins get beat up even with the best care......
Sometimes the long fin males can have fin issues due to the filter/water movement as well as space...some...not all....these abnormally long delicate fins can get really tattered with use from swimming and the water movement....kinda like a flag in the wind effect.......
You may need to turn off the filter and add some IAL or dried Oak leaf to get him healed up and fins toughened up some.....sometimes the tannins will help toughen fins and scale.....
Since you caught this early-he may not need a salt treatment for now-but I would increase the water changes to 50% twice weekly for a couple of weeks-along with removing the filter, adding a tannin source and increase nutrition by adding another food to what you are already feeding-good quality varied diet fed in small frequent meals.....if you have access to live mosquito larva-offer a few rinsed for one meal a day to boost protein and you can even roll the pellets in fresh crushed garlic juice too.
How many and what species of live plants do you have....
It can sometimes take weeks to month to get full re-growth/healing and sadly if it is partly related to water movement and/or space-it may be a long term issue and all you can do is prevent secondary infections
Here is some info that may help you understand more
http://www.bettafish.com/showthread.php?t=78317
Lovely fella....nice find....it is sad sometimes when the fins get beat up even with the best care......