Lump

[DracosMomma]

Hi all,

I have a male beta and yesterday when I was cleaning his tank, I saw that he's developed a lump on his left side. It has scales on it and it looked like someone slipped a small pea under his skin. He's listing to one side when he swims and I'm really worried about him.

I looked up beta fish lumps online and some say it could be a tumor and some say it could be constipation. I tried to give him a thawed pea, but when I dropped it in his tank, it bounced off his head like a basketball and now he doesn't want it. (I think I did fed it to him wrong.)

Here are his specs:

Only fish in the tank.
5 gallon tank.
Has heater and filter.
Listing to one side.
Healthy appetite.
Hides behind his favorite Roman columns but will come out to flare at me as usual.

Please help. This is my first beta and I don't know how to fix him.

[Kim]

Could he have injured himself on anything? Is there any way to get a picture? That would be the most helpful, because a lump really could be anything.