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If you’ve ever seen a fish jump out of your aquarium, it can be quite a shock, especially if they land on the floor and then struggle to breathe before your eyes. So why do fish jump out of the tank?

It’s actually surprisingly common for fish to jump out of an aquarium, especially when it’s managed by an inexperienced aquarium owner. There are several answers to the question, and some are more simple to solve than others.

So let’s minimize the chances of it happening to you, by looking at the reasons why fish jump out of the tank, and what you can do stop that behavior.

Why Do Fish Jump Out of the Tank – The Main Reasons

It can be quite shocking to see that one of your fish jumped out of their aquarium water. Even more so if they’ve done it while you are not around, and you have walked into the room to see one of your beautiful fish dead on the floor.

What is it with these fish and such kamikaze behavior? Why would any creature rationally jump to its death?

Well, the point here to understand is that they aren’t considering it as jumping to their death. They are trying to escape the environment they are in because it’s damaging. On top of that, some fish species are more genetically prone to jumping behavior, due to their original surroundings.

1. Unhealthy Water

If you are in an unhealthy environment, you try to leave it as soon as possible right? Well, fish are exactly the same.

Unhealthy water means they are struggling to breathe and function, so they are programmed to try and seek escape from that area.

It could simply be a lack of oxygen in the aquarium, which could be happening for a number of reasons. Maybe not changing the water frequently enough, perhaps you need to inject more oxygen, or perhaps you’ve just got too many fish for the size of tank.

It could be that there is algae in the tank, which can make the water very unpleasant, and also sap the oxygen from it.

Or it could be that something you have put in the tank, like driftwood, is leaking toxins into the water. This is very common if it’s not treated before it is put into the aquarium.

And on top of that, you could have higher levels of nitrates and ammonia than is healthy. You can’t see this, but you should be monitoring it regularly.

Any one of these reasons, or a combination of them, could be the reason why your fish are contemplating escape.

2. Not Enough Oxygen

One of the main reasons is going to be a lack of oxygen generally, mainly for the reasons we’ve just talked about. You can spot a lack of oxygen by looking at your fish. If they are struggling to breathe, which can become evident under close observation, then it’s a no-brainer.

If your fish has jumped out of the tank, the first thing to look at is cleanliness and oxygen levels. Look at the size of the tank, and look at the amount of fish in it, is it simply that oxygen is being depleted too quickly?

You see, fish don’t have lungs that can breathe the way we do, they need dissolved oxygen within the water to breathe properly. Not being able to breathe properly starts to stress the fish, causing them to take drastic action.

This is why it’s important to make sure your tank is clean, the water is frequently replaced, and also oxygenated by cycling it. You could also look at putting plants in that water oxygenated better.

Jumping to the highest level – goldfish jumping in a bigger bowl – aspiration and achievement concept. This is a 3d render illustration

3. Temperature

Another big reason for fish jumping out of the tank is that the temperature is too hot, or too cold. Are you sure you know what the ideal temperature range for the type of fish you have is?

Apart from knowing the climate your fish require, you also need to monitor the temperature every day. Is the tank fitted with at least one accurate thermometer? You need one on the outside and one on the inside.

Is the tank next to a radiator, in direct sunlight, or near a door, or window, that is frequently open? It’s little things like this that you might miss, which could be dramatically changing the temperature in the tank, dramatically enough for sensitive fish to struggle with.

So if your fish has jumped out of the tank, don’t just throw it back without checking the basics around the temperature in the tank.

4. Escaping From Threat

This is a reason for fish trying to escape the tank that is often overlooked, although it’s not as common as escaping a dirty environment, or a lack of oxygen.

But if you have ensured the tank is thoroughly clean, and the water at the right temperature, then another reason could be that the fish are escaping from threat.

If you have mixed species, or even if you have the same species, then one aggressive fish could be traumatizing others in the aquarium. Look out for aggressive behavior, unusual responses, swimming patterns, and things like that.

Again, if the tank is too small for the amount of fish you have, then the constant crowding with no ability to escape can also cause fish to leap out.

But it could also be a general response to a perceived threat. If your tank is somewhere where movement happens, for example, children running around, then that could be upsetting the fish. If the tank does not have enough hiding spaces or blind spots where they can get away from that movement, then that could also trigger a traumatic response.

So if all the other reasons have been covered, then try de-stocking, rearranging the tank, and maybe putting in extra plants to allow more space to hide.

Scientific Reasons Fish Jump Out Of Water

It’s actually been found through scientific studies, that fish escaping from their tank is not just a random act of desperation on an individual level.

One study in the USA, that focused on guppies, looked at the act of jumping from the tank. They set up recording equipment to look at what took place prior to the fish escaping the tank.

What the researchers found is that it was a very deliberate act. The fish would make sure they had the space to escape the tank, after swimming about for a while, obviously sizing it up. They would then give themselves space, and get up speed to make the attempt.

So the fish was well aware of its surroundings, its limits, and how to escape. This means that fish jump from the tank on purpose, partly for reasons of distress, but also because of genetic programming.

goldfish jumping

Some Species Are Genetically Programmed To Jump

Studies have found that some fish demonstrate the behavior of jumping on a regular basis.

Guppies, as we have already discussed, are prone to jumping from the tank. But it wasn’t to escape predators, nor is it about trying to get food. It appears that guppies often do it to look for freshwater. That goes back to the environment these fish are from.

Another species that does this is the betta fish. Their natural environment is shallow water, swamps, paddies, and even ditches in Thailand. The active jumping appears to be to do with needing to change the environment. It’s a deliberate act, a gamble, to try and find better water.

In fact, the betta fish breathe slightly differently to achieve this. As the water dries up in its environment, the fish knows it has to jump, and it can do this several times. They are attempting to get lucky in finding more water or die in the attempt, knowing that their current environment is unsuitable in the longer run.

To aid this dramatic behavior, the betta fish has evolved with a breathing organ, called a labyrinth, which actually enables them to breathe out of water for very short periods of time, allowing them to make repeated jumps.

So there’s not a lot you can do if you have tried everything else, but if you have a species like guppies or betta fish then all you can do is to try and limit this behavior You have a couple of options here:

  1. Simply cover the top of the tank so they can’t escape
  2. Buy a bigger tank so the water level means they can’t physically make the jump

Fish Jumping? Check These Things

As you can now see, there are plenty of reasons why your fish might be leaping from the aquarium, being prepared even to die in the attempt.

Regardless of why they are doing this, it’s a sign they have reached the point of desperation, a point of no return to escape the environment they are in. Particularly sensitive fish could also jump before the reason becomes obvious, they just perceive the environment is deteriorating, especially in certain species.

So make sure that if you find a fish that’s jumped from the tank, you check the following:

  • That the tank water is oxygenated
  • That the water is within the right temperature range for the species you have
  • That there are plenty of places to hide and segregate within the tank
  • You don’t have a noisy environment, or one with lots of movement, around the tank
  • Check the fish aren’t fighting, or that there isn’t an aggressor
  • Know the traits of the species you own
  • Check your equipment, and make sure the aquarium filters are working
  • Ensure that you test the levels of ammonia and nitrates

Once you make sure that the environment is definitely perfectly habitable, then your only other options are to lower the water level, buy a bigger tank, or put a lid on the tank you have.

If you like the article above, here are some other similar articles you should check out!

Are Fish Tanks Good for Anxiety?

How are Glofish Made?

What Makes Fish Grow Faster? Top 5 Reasons Why


Hi, my name is Jordan. I've been in the fishkeeping hobby since my childhood. Welcome to my blog where I help fishkeepers enjoy the hobby by offering free guides, advice, & product reviews. Read more...