When a goldfish stops eating, this is often the first sign of a problem with your fish. While the lack of an appetite can be a sign of illness, often severe, it can also be a sign that your fish notices something wrong in its world. If you know the reasons why a goldfish stops eating, you have a good chance of locating the problem quickly and making the necessary changes to help your fish.
Environmental effects alter a goldfish's eating patterns, preventing your fish from eating its normal diet. These include unclean water, the presence of chlorine in its water, a dirty water filter or another dead fish in the tank with your goldfish. Check the water quality in your tank, making sure that you recently added water conditioner to your fish tank and the filter is working correctly. Look at the water in the tank, and check to make sure it is clear. Also look at the glass around your tank, checking to see if the glass is collecting stains or becoming discolored.
Your goldfish can become ill, reducing or eliminating its appetite. Look for symptoms of illness in your goldfish, such as any unnatural growths on its body, small white spots, raised scales or unnatural bloating. It may also have inflamed gills, gills that flicker at an increased rate, bleeding on its body or rotting around its fins or gills. Look for behavioral changes, such as listless floating or constant hiding. Call your local veterinarian if you see any of these symptoms in your goldfish.
Goldfish react negatively to food that is no longer good. Check the expiration date on your fish food and make sure it is up to date. Also, check the conditions where you keep the food in conjunction with the instructions on your fish food. Some fish food requires you to keep it at a certain temperature or away from direct light. Keep your fish food stored in a safe place, noting the specific needs of the food.
A goldfish requires a day, sometimes two, to transition between one environment and another. This includes when you first move it into your fish tank, as well as when you move it into a temporary bowl so you can clean its tank. Give your goldfish a few days to regain its appetite after a move, while it grows accustomed to the changes. If the lack of appetite persists after a few days from a change in environment, call your veterinarian and consider other possible causes of its lack of appetite.