Why Do Fish Jump Out Of Their Tanks? | Aquascape Addiction

Why Do Fish Jump Out Of Their Tanks?

We cover the 4 main reasons why your fish might be jumping out of their tank, what to look for and the solutions to stop it happening going forwards.

Why Do Fish Jump Out Of Their Tanks?

If you have fish in a home aquarium, you might have seen fish jump out of the tank. Usually, when fish jump in the wild, they are trying to escape something, usually with the aim of jumping into a new body of water. However, in a home aquarium, if your fish are jumping out of their tank, they are going to land on the floor.

This is of course not ideal as your fish won’t survive for long out of the water. Some people might think that this jumping behavior is normal, but it is certainly not. Why do fish jump out of their tanks is what we are here to talk about today.

Why Your Fish Is Jumping Out Of Their Tank

There are a 4 main causes as well as solutions to these causes, let's look at each in more detail;

1. Not Enough Oxygen

One of the biggest reasons why fish could be jumping out of the tank with the hopes of finding a new home is due to a lack of dissolved oxygen in the water. While most fish do not have any lungs to breathe gaseous oxygen, they do need a lot of dissolved oxygen within the water in order to breathe. If your fish cannot breathe well due to a lack of oxygen, it might jump out in the hopes of finding somewhere with more dissolved oxygen.

Now, a lack of oxygen in the tank can occur due to several reasons. First off, if you have a really heavily stocked tank with way too many fish, there won’t be enough oxygen in the water. Your fish will literally be competing and fighting with each other for the right to breathe.

In this case, the solution would be to have less fish in the same size tank, or you could get a bigger tank too. If you do not feel like doing either of these things, adding an air stone to the tank is the other solution. Air stones are specifically designed to oxygenate and aerate the water so fish have ample amounts of dissolved oxygen to breathe.

Another problem could be algae. Algae tend to use up a fair amount of oxygen under the right conditions, which is a problem of course. If your fish are jumping out of the water, and there is algae in the tank, it could be the algae that is literally suffocating them. In this case, you will need to remove algae from the tank to give your fish room to breathe.

2. Too Much Ammonia and Nitrites – DIRTY WATER

Another thing that could cause your fish to jump out of their tank is an elevated level of ammonia, nitrites, and nitrates in the fish tank. In other words, if the water conditions are not ideal, your fish will attempt to leave in search of a better home.

Ammonia is a really big problem because even minimal amounts can make fish really sick and kill them. The first thing you should do if your fish are jumping out of the tank is to test for ammonia and nitrites.

If the levels are anything above the recommended amount, which in this case is zero, you know what the problem is. High ammonia levels are usually caused by decaying matter such as fish waste, uneaten food, dead fish, and decaying plants.

Therefore, some solutions to cut down on ammonia include performing regular water changes, not overfeeding your fish, regularly cleaning out waste and debris, and always making sure that the water is as clean as can be (more on lowering ammonia levels on this article).

At the same time, you absolutely need to have a good biological filtration unit in place. Biological filtration media serves to break down ammonia and render it harmless. If you do not have a bio filter, or if it is not working properly, you have got a big problem. Make sure to have a properly functioning biological filter.

Make sure to keep the media clean and replace it when necessary. Using a beneficial bacteria supplement could help too. Less than ideal water conditions are a big cause of fish jumping out of their tanks.

3. Temperature

Another factor that is related to water conditions which could make your fish jump out is temperature. Fish are generally pretty sensitive to temperature changes and pretty much all of them need a certain water temperature to be happy and to survive. If the water is way too cold or hot for your fish, they may jump out in search of better temperatures.

Of course, they will do this in the beginning, that is if the cold or heat has not already rendered them incapable of doing so. Check the temperature of the tank water and be sure to know what temperature is required for your fish.

If the water is too hot or cold, you know what the problem is. Taking steps to remedy the situation is what you will need to do.

4. Lack Of Hiding Places & Space

Now, these causes are less documented and harder to prove, but they might still be the case. If you have your fish in a really small tank, way too many in a space, they will feel cramped and might feel the need to escape to a place with more room to swim.

The case could also be that there are several types of fish in the tank which do not get along. Although this seldom happens, smaller fish that are threatened by other more aggressive or larger fish could try to escape the tank to get to a safer place.

If there are not enough hiding spots, like plants and caves, threatened fish could try to make a break for it.


As you can see, there are many reasons why your fish might be jumping out of their tanks. If they are doing so, you will have to keep an eye on things, make sure the fish are not crammed into a spot that is too tight for them, make sure to have a well working filter, test for ammonia, and all of that other fun stuff too. It might take a bit of trial and error to find out why your fish are jumping out of the tank, but if you want them to stop, you will have no choice but to engage in a bit of guessing game.