Betta fish diseases

Question
I saw you have a lot of experience with betta fish and I'm hopeful you can provide me some guidance.  I have a female betta fish that is about two years old.  About a month ago she seemed to acquire a small lump under the left gill. Over the last month it has grown in size. There seems to be a little white under the gill but, for the most part, it is under the gill and not on it. Do you happen to have guidance on what it could be or what I might do for it?
Thanks!!

Answer
Helo,
A bump on a Betta could be internal Parasites (which usually happens to bettas who eat live food,) it could be a tumor, which is or is not cancerous, it could be your water chemistry, or it could be a bacterial infection. It is always hard to tell what a lump is on a betta.  First check your water to see if you have ammonia, and nitrates in it.  Ammonia is the number one killer of fish.  If you have ammonia, and a high level of nitrates, this could be the cause. Do a major water change always with a good conditioner, to get the nitrates down, and the ammonia down to zero.  Clean water is so important to bettas, and other fish.  Her water should be between 78 and 80 degrees.  When a betta is cold, she becomes sick.
I would treat her with an antibiotic to see if this helps her, but before treating her, make sure she doesn't have ammonia in her water.  Kanamycin, Tetracycline, or Furan2 are good antibiotics.  After the treatment, if your betta is still the same, there isn't much more you can do.  Always keep her water free from ammonia, and do your water changes. Vary her diet, feeding her small amounts 2-3 times a day.  An example...2 pellets for one meal.  We must always remember that her tummy is the size of her eye.  This is so important.  I have seen bettas live a long time with a lump. I wish I could be more helpful, but diagnosing a lump is very difficult.  
If she is eating, this is a good sign.  A sick Betta stops eating.
It is the white that you see that bothers me.  Maybe with a antibiotic treatment this will go away.  I hope she does pull through, and that the white stuff disappears.  If only the lump remains, then like I mentioned, she may live a long time with the lump, like we do when we have a small tumor.
Hope this helps
Lynda