From what I heard it's a form of genetic defect and/or skin cancer so there's nothing you can do about it. You can use some iodine to treat the area...
A couple of issues here. That layer of composting leaves and debris is probably filled with chemicals that will kill the fish if the sediment on the...
So this is my goldfish Rangli. He's about 5 years old or so. First photo is today. Second one from around Feb. Small yellow spot where wound now is....
Keep an eye open for ammonia not that it's going to spike but it's not going too hurt to check it every other day for atleast a week and I would cut...