Betta Problems

[PrettyFishies]

I have a Betta who's been in his 2.5 gal tank for at least 6 weeks w/o a light. We just replaced it. Now, I notice that he has what appears to be a fungal growth near his left eye. He's active, eats everyday, but I'm worried about this. Any ideas?

The tank has a filter and gravel bed.

 

[whitetiger_CJ]

Treat the tank for fungus. there are many products available.

 

[Meredith]

How often do you do water changes? Is there a heater on your tank?