Bug Eyed Goldfish

Question
I somehow inherited a black bug eyed goldfish a couple of years ago and everything has gone well until the last few days.  I noticed a couple of days ago that one eye appeared larger than the other. It seems to have swollen more and today that side of his face is all swollen and looks like it will pop.  Anything I can do for him?
He is alone in the tank, never comes in contact with other fish, and I have not changed anything in his diet, the tank filter system or anything else.

Thank you for any advice.

Answer
Hi Carol,
  Unfortunately I am no expert on goldfish, and in particular on some of the more bizarre forms, so I cannot answer your question directly. Have you been doing regular weekly water changes? Ideally, you should be changing 25% of the water in his tank once a week, every week to keep him happy and healthy.  That is the single-most important thing you can do.

-- Ron C.
  rcoleman@cichlidresearch.com
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