Goldfish Constipation is a serious complication of incorrect feeding, overfeeding or food that doesn't agree with your fish. If you notice you have a Fat Goldfish in your tank be concerned about this fatal illness.
Symptoms: Appears bloated, very inactive, lies on bottom.
Treatment: Remove fish from main tank. Do NOT feed your fish for up to 5 days or until it begins to be active again and resumes normal behavior. At that point feed it freeze-dried food for one week. It may then be returned to the regular tank.
This is notably an increased problem in Ryunkins, Veiltails and Pearl-Scale types of goldfish.