Red 'Tumor' by anus

[Super_Blueberry]

One of my pristellas has what looks like tumor coming out (or at least very near) to his anus. I tested my water this morning and it came back 0, 0, 5. He is swimming and acting normally, and other than the tumor, there are no physical problems I can see. I usually fast my tanks on Sunday, but didn't this week. I'm fasting today to see if it clears up, so I can't tell you if he is eating. Any ideas what this could be? What are my treatment options?

Thanks as always!

 

[nwsharksfan]

Hemorrhoids? Do they make tux for fish?