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Home > Goldfish > Why Your Goldfish Is Not Eating: 10 Vet-Reviewed Reasons

Why Your Goldfish Is Not Eating: 10 Vet-Reviewed Reasons

Goldfish with dropsy or swollen scales and bellies

As goldfish owners know, these fish love eating. Goldfish are omnivores that can and will eat just about any edible item that fits in their mouth. Because of their love of food, it can be very concerning if your goldfish suddenly stops eating, especially if you’re offering treats and favorite foods. Here are the main reasons why goldfish stop eating and how to fix them.


The 10 Reasons Why Your Goldfish Is Not Eating

1. Water Quality Issues

The top reason for any issue with goldfish is poor water quality, which is often due to poor tank maintenance or a lack of knowledge of how to properly care for the tank. Within an aquarium, there are multiple things that can impact water quality, including ammonia, nitrite, nitrates, phosphorus, overstocking, dead animals, and some types of algae. To properly maintain your tank, you need to invest in a high-quality water testing kit, as well as a filtration system that is rated for the size of your tank, at a minimum. Perform routine water changes and water parameter checks to maintain good water quality.

goldfish in dirty tank
Image by: JenJ_Payless, Shutterstock

2. Low Oxygen

Sometimes, we forget that we can become low on available oxygen. This typically happens if your tank lacks filtration and air stones. Low levels of available oxygen in the tank will make it increasingly difficult for your goldie to breathe. In humans, hypoxia (low oxygen) leads to things like dizziness, weakness, and confusion. It’s reasonable to assume that goldfish are also negatively impacted by hypoxia, which can lead to a lack of appetite and refusal to eat.

3. Toxins

Although toxins in the water are technically a water quality issue, this is referring to toxins that got into the water from an outside source. If you put your hand in the tank with soap or lotion on, used cleaning products by an open tank, or your child poured something into the tank, then your tank may have toxins in it. Toxins can range from irritating to deadly for goldfish, so it’s extremely important to ensure that only appropriate things go into the tank. When adding anything new, like pebbles, plants or accessories, be sure to rinse them thoroughly before placing them in your tank. but do not use detergent.

4. Stress

Goldies may be quite hardy fish, but they can still become stressed. Stress in fish can be caused by a variety of things, like bullying, poor water quality, illness, inappropriate tank mates, and leaving the tank light on all the time. Usually, stress can be remedied by removing or fixing the source of stress, which will likely encourage your fish to start eating again. Make sure your goldfish’s tank is appropriate and that they are healthy to prevent stress.

Man cleaning a dirty fish tank
Image by: victoras, Shutterstock

5. Cold Temperatures

Goldfish are coolwater fish, and they can survive water temperatures as low as freezing. However, their ideal tank temperature can range between 60–72°F. While they are tolerant of temperatures outside of this range, their bodies do something interesting around 50°F.

When the water reaches this temperature, goldfish enter torpor, which is a semi-hibernation state that results in a decreased metabolism. If kept in cold temperatures for an extended period, your goldfish likely won’t need to be fed because they will lack the ability to actually digest their food. If you feed them while in torpor, your goldfish may refuse to eat altogether.

6. Stale Food

Just like with human food, fish food has an expiration date. It is shelf stable for quite a while when unopened, but most sources recommend throwing away open fish food after 6 months. Old food can become rancid and lose nutritional value, taking the yummy taste with it.

If your goldfish’s food is old, they may stop eating it, especially if the food has gone bad. If your fish eats a gel food, like Repashy, then it’s important to read the package for how long the food is good for after opening and after preparing it.

7. Blindness

Fish can go blind due to damage to the eyes, and some fish even lose their eyes due to popeye disease. Goldfish have a sense of smell that helps them find their food, but they also use their vision. For blind Goldies, finding food can be difficult. They’re especially at a disadvantage when sharing a tank with other fish, since blind fish may need more time to find food. If your goldfish is blind and not getting to eat or not seeming interested in food, try to separate them at mealtimes with a colander or breeder box to give them a chance to eat.

Goldfish sick with tumor
Image by: Jaclyn Peer, Shutterstock

8. Too Much Space

Even though too much space is generally not considered a bad thing, a large tank can make it difficult for your fish to find food when you put it in. Try to create a routine of when and in which part of the tank you feed your fish, so they always know how to find their food. Floating rings and other tools can also be used to keep the food confined to a small area so your fish doesn’t have any trouble finding it.

9. Medical Conditions

Goldfish can develop many medical conditions that may cause them to not eat, including tumors and organ failure. They can also become constipated, and while constipation in goldfish is often blamed for virtually every goldfish issue, if they truly become constipated, it can stop them from eating.

Goldfish don’t have a stomach, so when they eat their food, it is simply digested as it passes through the digestive tract. When constipated, food may stop moving properly, leading to bloating and discomfort.

10. Overfeeding

How many times per day are you feeding your goldfish? Most goldfish do well with being fed once daily, but some keepers only feed every other day. Any food left in the tank after 5–10 minutes should be removed from the tank to avoid overfeeding and an accumulation of food waste, which can affect water quality. If there is leftover food after meals, then you’re feeding too much food at once.

Goldfish will “beg” for food at the glass of their tank, but they simply shouldn’t be fed multiple times per day. Since they are foragers, you can provide leafy green veggies or algae sheets in the tank for your goldfish to “forage” throughout the day. This will keep them occupied and prevent begging for food.



If you’re struggling to determine why your goldfish isn’t eating, then it may be time to talk to a vet who specializes in the care of fish. Goldfish can survive quite a while without eating, particularly at cold temperatures, but the refusal of food for more than a couple of days under normal conditions should be cause for concern. Not eating indicates that there is some kind of underlying issue with your fish that needs to be addressed.

Featured Image Credit: Pavaphon Supanantananontm, Shutterstock

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