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Why Do Fish Jump Out of Their Tanks? (8 Main Reasons)

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By Lindsey Stanton

fish jumping out of bowl

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 and jump 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. So, why do fish jump out of their tanks?

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The 8 Reasons Why Fish Jump Out of Their Tanks

There are eight primary causes as well as solutions to why fish jump out of tanks. Let’s look at each one in more detail:

1. The Tank Is Too Small

goldfish in a bowl
Image credit: Unsplash

Fish appreciate a great deal of space. When confined to a small and cramped space, it will attempt to flee its living conditions by jumping out of the tank. A fish should be given as much space as you can afford and upkeep. Fish become uncomfortable when there is no room to swim appropriately.


2. 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 require dissolved oxygen within the water 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, 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 be competing and fighting with each other for the right to breathe.

In this case, the solution would be to have fewer fish in the same size tank, or you could get a bigger fish tank. 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 designed to oxygenate and aerate the water so fish have ample amounts of dissolved oxygen to breathe.

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


3. Too Much Ammonia and Nitrites – Dirty Water

goldfish in dirty unclean tank
Image Credit: Chaikom, Shutterstock

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 quality/conditions are not ideal, your fish will attempt to leave in search of a better home. Ammonia is a 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 to ensure water quality is ok.

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 in 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 biofilter, 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.


4. Undesirable Water Temperature

Another factor that is related to water conditions that could make your fish jump out is water 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 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.


5. Aggressive Tank Mate

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Image Credit: Solarisys, Shutterstock

Some species of fish are territorial and do not get along with other fish. Keeping a fish that is unsuitable for community tanks will lead to fights, fin nipping, and aggressive chasing, which will leave your submissive fish no choice but to flee the tank from the tank mate.


6. Stress

Fish that are kept in a stressful environment with a variety of stress triggers will feel overwhelmed and escape out of the tank. Constant light changing distress, bright lighting over the tank, poor lighting for some time, noise, and constantly moving the tank will cause the fish to become stressed.


7. Fright

woman playing with pet goldfish
Image Credit: iordani, Shutterstock

Tapping the glass of the tank, knocking, and rough handling will cause the fish to jump out of the tank due to fright. A fish that is suddenly scared will instinctively jump out of the tank, mostly due to reflexes.


8. Lack of Hiding Places & Space

These causes are less documented and harder to prove, but they might be relevant. If you have your fish in a really small tank, 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 that 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.

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How to Stop Fish Jumping Out of the Tank

There are a few ways to stop fish from jumping out of their tanks.

  • Keep your fish in a spacious tank with lots of swim room both vertically and horizontally.
  • Keep an air stone and filter in the tank to ensure the water stays clean. Rinse all new gravel, as it is dusty, and regularly test the water for unsuitable parameters.
  • Do not tap on the glass or place the tank in a noisy and chaotic environment.
  • Purchase a secure aquarium lid to fit your tank’s design.
  • Keep the right species of fight together to avoid your fish from jumping in an attempt to flee from its tank mates.
  • Always cycle a tank before placing fish into it (the nitrogen cycle).
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Image Credit: Pixel-Shot, Shutterstock

As mentioned above, jumping out could be a sign of a deeper issue, such as water that is too warm or too cold, not enough oxygen in the water, the tank is too small, or too many tank inhabitants.

So, to find the right solution, you first have to figure out what the underlying problem is.

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Conclusion

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 the fish, make sure they are not crammed into a spot that is too tight for them, ensure you have a working filter, test for ammonia, and maintain the water chemistry. 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 a guessing game.


Featured Image Credit: Mikael Damkier, Shutterstock

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