Hello. I’ve had my goldfish for a few years. They live outdoors in a 100 gallon water trough. Late August I noticed one of my fish had a discolored bulge near his tail. I left him in the tank a few days when it was first thought to be a contusion but then moved him in to a 20 gallon hospital tank with an Aqua Clear HOB filter where he’s been (alone) ever since. In the ensuing months, I’ve tried treatments including erythromycin and general cure, always attempting to do frequent water changes. Lately, I shoot for 2 to 3 water changes a week and dose with melafix between changes. His appetite is good and he is active, but I think he is uncomfortable since he usually has his tail over an air stone that creates an abundance of tiny bubbles. Does anyone have a possible diagnosis or thoughts on effective treatment?
The last photo is from early September just before I removed him from the community tank. The other three photos were taken today.
The last photo is from early September just before I removed him from the community tank. The other three photos were taken today.