fish are jumping out of the tank

Fish jumped out from aquarium: Scientific Truth from a veterinary

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Ornamental fish may jump from the fish tank and it happens quite a lot with some aquarists. If you are one of them then you should know jumping from water is not a natural habit of fish. It happens only when they feel uncomfortable in the fish tank. Now there are some reasons why fish are jumping out from aquarium that you must know

Fish may jump out of an aquarium because of an uncomfortable situation according to a veterinarian. Generally, lack of space and deficiency of oxygen are two primary causes of this situation inside of an aquarium. However, due to additional oxygen guppies, mollies, etc. may jump. 

This answer is certified by Udipta Roy, M.F.Sc. (JRF), PhD Scholar, Aquaculture, ICAR-CIFE, Mumbai

This couple of sentences may give you a brief idea about this topic. However, you should know this topic in detail and that’s why I’m going to discuss the 7 most possible reasons why fish are jumping out of a fish tank. Let’s dive deep into the topic

Why are fish jumping out of the aquarium? 

Why are fish jumping out of the tank
Why are fish jumping out of the tank?

Fish will not jump out of the aquarium without any reason. Either aquarium fish have faced some difficulty in living or it has seen any prey outside of the aquarium. Now you have to analyze before going to a conclusion. Let’s know these 7 reasons that you may face.

  • Deficiency of oxygen level 

Each and every fish requires oxygen. So oxygenation is a must for an aquarium. Now according to some veterinarians, fish may jump due to lack of oxygen in the water.

According to a source, the dissolved oxygen is required for an aquarium is from 5 to 7 ppm. If this quantity becomes less than 4 ppm then fish feel uncomfortable in the tank and tendencies of jumping increases with this situation. However, this oxygen quantity varies from tank to tank.

In addition, DO (Dissolved Oxygen) has a relationship with water temperature. Coldwater carries more dissolved oxygen than relatively warmer water. According to the source, stagnant water condition carries a comparatively smaller amount of dissolved oxygen than agitated water. Thus, if you have a good filtration system then this issue may not occur.

Read more:- How to Stop Fish Attacking Others in Aquarium: 90% People don’t know this

  • Lack of space in the aquarium

Generally, fish come from a huge water body and when they get a small fish tank then the chances of jumping out from that aquarium increase.

However, it depends from species to species. If your aquarium is not overstocked then this issue may not arise from you.

But It may happen unknowingly. The general rule of thumb of stocking fish in an aquarium is “one inch per gallon“. However, this rule of thumb has some errors because this rule does not consider the filtration system, decoration and other materials in an aquarium.

This rule is good for slender-bodied fish like guppies, zebra danios etc. However, if you have goldfish or cichlids then you should not follow this rule just because of its high growth rate and high waste production. In this case, you can follow one inch per two-gallon of water for safety.

  • High ammonia and nitrite level 

Ammonia and nitrite are two very harmful elements for an aquarium. If an aquarium consists of a small amount of ammonia or nitrite then that aquarium will not be liveable for fish.

Now this situation may create problems for your aquarium too, due to high ammonia or nitrite levels. To check the level of ammonia and nitrite you can use the Ammonia checker.

If your aquarium fish are jumping then you must check ammonia and nitrite level daily. A few fluctuations of these elements can cause bad circumstances for the aquarium fish. So you must take action immediately according to the data.

  • The wrong temperature of the aquarium 

Fish can jump out of the aquarium due to the fluctuation of temperature also. A wrong temperature always creates discomfort for the aquarium fish. So if you want to keep all of your fish healthy and happy then you must look after them by maintaining the right temperature.

Maintaining the right temperature is not difficult. However, having an excellent heater is a must for an average-sized aquarium. From 23°C to 26°C is a suitable range of temperature to keep an aquarium.

You may see a specific temperature for a certain type of fish. But you must know there is no hard and fast rule of setting a temperature. Fish can tolerate a vast range of temperatures. However, fluctuations in temperature are harmful to each and every species of the aquarium. You must prevent this by fixing the heater.

  • A natural characteristic of Labyrinth species 

Labyrinth species like betta and gourami seldom jump out of the tank. It is their natural behavior because they can absorb oxygen from air directly. It means betta and gourami fish can continue their respiration process in both air and water. It is possible due to its labyrinth organ. Thus they jump out of the tank to take oxygen from the air.

However, it should not happen frequently. If you see that your betta or gourami is trying to jump out of the tank once and twice then you must check the other water parameters. For betta fish, it happens quite a lot due to the lack of space in the aquarium or fishbowl.

  • Excess oxygen level

For keeping some aquarium fish you are not required to oxygenate the tank externally. Those fish can live in stagnant water conditions too. These fish are generally considered hardy fish.

If you have Mollies Platies or Swordtails in your aquarium then you do not require oxygenating the tank differently. Due to excessive oxygen, the tendency of jumping out of the tank may increase. For those fish, the excessive oxygen may create an uncomfortable situation inside of the tank.

Read Here:- Can We Keep a Fish Tank in the Dark? Know Scientific Truth 

  • To prey insects outside of the aquarium 

Some aquarium fish species have the natural tendency to jump out of the aquarium. Arowana sp is such an example of it.

These types of fish try to prey on insects outside of the aquarium and that’s why they jump out of the aquarium. If your aquarium has some floating live plants then the chances of jumping out of fish will increase. It is because floating live plants attract different types of insects.

How to stop fish from jumping out of the tank?

Generally, aquarium fish try to jump when they feel discomfort. Now to stop their jumping tendency, having an excellent quality of water and good tank condition is a must. 20-30% water change is recommended once per week to maintain a healthy aquatic environment. 

Not only that, but if you add a sufficient amount of hiding places then it may prevent this tendency of fish. Moreover, you should keep a fish tank in a peaceful place. This will help your fish to realize the safety of their living place. You must remember fish try to jump when they feel anxious about anything. Thus it is your responsibility to reduce the chaos externally. However, if an aquarium is placed in the middle of the hall room or any busy place then it is better to cover it up completely.

Read Here:- Fish is Hanging Around Filter: 7 Reasons According to Experts


In this article, we have discussed the jumping tendency of ornamental fish. As a whole, fish jump out of the tank due to a lack of comfortable position of living. When they feel anxious or stressed then only fish try to jump out.

However, this is not completely true. Some fish like Arowana sp have a tendency to prey on insects outside of the tank and that’s why it jumps. Betta and gourami are labyrinth species and so they jump out of the tank seldom to get more oxygen for them from the air. But when you notice this kind of behaviour of your fish then you must take some precautions which have been discussed here.

So best of luck & happy fishkeeping 🐟

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