Do Goldfish Eat Each Other

Goldfish are beautiful pets that enhance any room in the house, and owners can quickly become enchanted with the different colors and patterns that the fish can showcase. So much so, in fact, that it can be difficult to know when to stop. 

If you have enough room in your tank for another goldfish, then why not opt for two so that your pet isn’t lonely anymore? Well, there is the small problem of the fact that goldfish have been known to pick on smaller fish and eat them. 

This is also true for smaller goldfish, so if you have a large and dominant goldfish in a tank before introducing it to a new baby, you might find that it’s missing just days later. However, not all hope is lost! There are a few ways in which you can prevent your goldfish from turning on each other and feasting.

Below we’ll be looking into how to stop goldfish from eating one another so that you can keep them in the same tank, living in perfect harmony. 

Will every goldfish eat another?

Goldfish are not cannibals at heart, which is why the pet stores don’t offer up a warning about keeping goldfish separated. It is completely feasible that you can keep your goldfish together in one tank without them eating each other, as long as you keep them well fed. 

If a fish is hungry, they’ll find food wherever they can. If their housemate just happens to be the only food source in sight, then so be it! To avoid this from happening, you should try to opt for goldfish that are around the same size. 

Your goldfish will grow to the size of your fish tank, so the larger the tank, the larger your fish will become. Waiting until your goldfish grows into a 25-gallon tank before introducing a baby is a recipe for disaster, so don’t do it. 

Goldfish also don’t have those squishy feelings that humans might get when they see a baby. If a goldfish were to lay eggs they would most likely eat them. Should any eggs survive, the baby fish would also become dinner for their parents. 

So, goldfish are more likely to eat each other if there is a clear size difference between them. 

How to prevent goldfish cannibalism?

First thing’s first, make sure that the goldfish are the same size if you’re going to be putting them in the same tank. You can either do this by purchasing them at the same time and age, or you can match the size of your new goldfish to the existing one. 

If one of these goldfish falls pregnant, it is vitally important to separate the fish from the others in the tank with a breeding tank. This will allow the babies to be separated from the mother so that she doesn’t feast on them while you’re not looking. 

Once you’ve ensured that the same goldfish are the same size, you need to prevent them from becoming hungry. If you don’t feed your goldfish enough, they will begin picking at the tank and anything in it. Including their friends. 

Goldfish are traditionally herbivores and therefore are happy with high-quality protein and carbohydrates. This can often be found in goldfish pellets and flakes, so make sure that you stock up and feed them two to three times a day. 

This prevents them from getting too hungry between meals. You should also use as much food to allow them a two-minute feeding window. Any more than this will be wasted and cause the tank to get dirty quicker.  

How many goldfish can be kept together?

One goldfish should be kept in a tank that is no smaller than 20 gallons to allow them plenty of space to grow. If you want to add another goldfish, you’ll need to increase the size of the tank by another 10 gallons. So, while there is no set number on how many goldfish you can keep in one tank, you will have to work out the correct size. 

Opting for a tank that is too small for multiple goldfish will increase the likelihood of cannibalism as well, so don’t overlook this vital consideration. For example, if your tank is 50 gallons, you will be able to house four goldfish in one tank. 

If you’re introducing smaller fish into a tank full of established goldfish, a smaller tank will offer the new pets fewer places to hide out until they’re larger. Therefore, they’ll be less likely to survive from their predators in a small tank. 

Goldfish are notorious for being dirty and messy. They expel a lot of waste and therefore their tanks get dirty quickly. This means that they need more water to prevent their dirt from stewing too much. A small tank will need to be cleaned much more regularly than a larger tank, and this is just another incentive to choose the right size of tank for your goldfish. 


To summarize, goldfish can and will eat each other under certain conditions. However, goldfish are not natural carnivores or vicious animals. They can live together without any hassle, provided that you follow some simple rules. 

For starters, make sure that your goldfish are the same size wherever possible. This means that you should either purchase them from the same school or you should match the sizes of your existing goldfish. 

Babies should also be removed from the tanks and put into their own tanks to avoid cannibalism. The size of your tank will also affect whether your goldfish turn on one another. The smaller the tank, the more likely fish are to eat one another. 

Two goldfish should not be in a tank any smaller than 30 gallons to avoid this. Finally, make sure that you’re feeding your goldfish on a schedule. Two to three times a day offer them enough food to last them for two minutes. Following these tips and tricks will lower the chances of your goldfish eating each other substantially.