Goldfish with swollen abdomen, but appears well

Question
Dear Jon, I have 3 goldfish (8 year olds)which have been moved from a large pond to a small one when I moved last year. The pond has a biological filter. I removed them into an indoor tank last winter as my new pond is quite shallow and noticed one fish had a swollen belly, but otherwise quite normal in behaviour. I released them into the pond in April and they appear to have had 2 spawnings.(10 little fish, 3 are much larger than the others) the goldfish with the large belly looks huge now, but is still eating and swimming around and has no raised scales. I'm thinking of isolating this fish, but don't know what's wrong with it to treat it.It looks like it could explode if I just leave it. I've searched the internet and can find nothing that helps me identify the problem. The swelling is symetrical, no eye bulging, just very large now. It's had it for 11 months. Do you have any ideas?

Kind regards

Monique

Answer
Monique, first of all I would like to apologize for taking so long to respond. Your fish could either have an internal bacterial infection which can be treated. It could also be normal depending on what type of goldfish you have. Your goldfish could also be "blocked up" so to speak and for some reason not releasing its eggs, if its a female. This could be especially so if you say that others have spawned in the past. I would like to invite you to take a look at this site as I normally do not prefer goldfish in any tanks of mine, and do not breed them.
http://ezinearticles.com/?Is-Your-Goldfish-Constipated&id=309809 I hope I have helped somewhat, and as always, if you may have any more questions about anything, don't hesitate to contact me again. Good luck.