Sick Betta

[Zuma]

My betta has something growing on his upper fin, as shown in the picture. He is still eating, but not as active as he normally is. I am not sure if this is a parasite or a tissue growth of some sort. If anyone could identify the problem and suggest a treatment, that would be greatly appreciated.

[Tango]

Hi,
Not sure what it is. It could be some sort of algea growth or somthing. Maybe do a 50% water change and check nitrate levels in the tank, take all the plants and rocks and and give them a good wash. It might help. I hope someone else can add a bit more advice :)