betta with bubble under eye

Question
Hi..I have had my betta for 2 1/2 years.  he is in a one gallon tank with air and filter.  My question is "he has developed a bubble under one eye, it's clear and doesn't seem to bother him,but it bothers me."  What can you tell me about this problem?
                 Ann

Answer
Hi Ann;

It may just be a fluid-filled sac under the skin that fish sometimes develop. If it starts to look reddish, fungused or otherwise infected you might want to try some medication. Keep his water very clean to help avoid infection and boost his immunity.

At Your Service;
Chris Robbins