[Canadian_Aqua_Farm]

It appears to be a fluid filled cyst. I have seen this in bettas on a couple of occasions. It will go away on it own but unfortunately it can be a reccuring problem.

 

[Canadian_Aqua_Farm]

It's nothing that you have done, just one of those things that can turn up every now and then. If I had to guess I would suspect that a virus is to blame.

 

[Canadian_Aqua_Farm]

Keep up with the regular water changes and feed it a variety of high quality foods to help keep the immune system boosted. Mysis are great and soaked in a HUFA supplement such as Selcon is even better.