Fish Diseases

Question
My Beta has a large round growth under his top fin.  It has been getting increasingly larger over the last few months.  I have successfully treated other diseases on my other fish over the years, but I have never seen this particular thing.  I did a little research and the closest thing that I could come up with is that he has an untreatable tumor.  I also went to Petsmart to see if they had anything that I could treat him with.  The lady that I spoke with said that she thought it sounded bacterial and that I should give him medicated food.  I was not convinced because nothing that I have read about bacterial infections sounds anything like this. I just wanted to know if you had any insight on this matter.

Answer
It sounds like a possible tumor to me as well. However, if you didn't want to risk being wrong, you could try the antibiotic Maracyn-Two available in your local pet store (I know for a fact PetSmart sells it). If you look closely at your fish, does it seem to have any red streaks on its body? If so, it could be a case of Septicemia, which can cause ulcers. If the Maracyn doesn't help, and your fish remains to act normal - I wouldn't worry about it too much. However, if something takes a turn for the worst please message back and we'll go from there.