I have a 3,000 gallon pond with 8 koi and 10 fantail and comet goldfish. All the fish have been in the pond for at least 6 months and some have been there since we built the pond .About a week ago one of the comet fish began to sit on the bottom at the far end of the pond. She comes to the surface with the rest of the fish when I come to the pond and she comes to the surface and eats with the rest of the fish. She then goes back to her spot. She is getting a swollen belly and it is getting bigger. Her scales are beginning to protrude a bit. Does she have eggs or is she sick. She doesn't swim abnormally or seem out of balance. She doesn't swim as fast or as easily as the other fish though. She is about 10 inches long.

None of the other fish are sick nor do they have any irregularities of any kind. The pond is several years old and I have not had any problems before except for an incident about a month ago: one of the other comets scraped himself on some rocks. I put him in a 70 gal isolation tank and treated him with Melafix for 2 weeks. His scrapes healed quickly. He has been back in the big pond for 2 weeks.

The pond has regular water changes, the filtration is good, and the water condition is good. There are some plants in the pond but perhaps not enough if the fish is wanting a place for eggs.

A female with eggs doesn't get protruding scales, this worries me and I agree with nabi that it probably is dropsy. Ans dropsy is caused by internal infections, infections show up in (very) stressed fish. And stress is most times caused by environmental issues.

Please keep us updated how things are going.