Why Is My Molly Fish Jumping Out of a Tank?

Why Is My Molly Fish Jumping Out of a Tank?

Molly fish are active swimmers that like to explore their surroundings and can often be seen swimming near the top of the water.

In some rare cases, they may jump out of a tank! This usually happens when tanks are too small, have poor water quality, or don’t have enough hiding places.

Also, molly fish are known to be easily startled, and a sudden noise or movement can cause them to jump out of the water.

In this article, we’ll discuss some of the reasons why your molly fish jumps out of a tank and what you can do to prevent it.

Do Molly Fish Jump Out of a Tank?

Molly fish jump out of the tank when they are not comfortable.

For example, dirty water, a lack of food, the tank lid being missing, or something else new that scares them causes them to leap out of the tank.

In addition, little tanks, overpopulation, and ammonia poisoning can all contribute to your molly fish’s inner athlete coming out.

How to Tell If Molly Fish Is Going to Jump Out of the Fish Tank?

When your molly is swimming erratically or in circles around something or circling the walls, it’s an indication that they’re going to jump.

This jumping behavior indicates that molly is attempting to flee their circumstances and is extremely scared.

Why Is Jumping Out of the Tank Dangerous for Molly Fish?

Molly fish will not get the proper environment they need to thrive if they’re outside the tank and will end up as dead fish.

Some other reasons why it’s dangerous for molly fish to jump out of the tank are:

  • They jump out of the water but can’t swim on land, so they’ll suffocate inside your house
  • They’ll get a bacterial or parasitic infection from the surrounding environment
  • They may be eaten by your other pet predators outside the tank
  • They’ll be exposed to extreme temperature changes that can kill them

When a molly fish jumps out of the tank, you must find a method to grab it and return it to the water as soon as possible.

To capture molly fish safely, you can use any small container, such as an empty bowl or cup with clean water.

Why Do Molly Fish Jump Out of a Tank?

1. Poor Water Quality

Molly fish are tough fish, but they still need clean water to thrive. If the water in your tank is dirty, your molly will jump out in an attempt to escape the poor conditions.

For example, food leftovers and fish waste decomposing in the water result in ammonia poisoning that causes burning skin and swollen gills.

Also, an increase in chemicals will limit oxygenation in the water, and your molly fish may start gasping at the water’s surface for oxygen.

As a result, molly fish jump out of the tank as a coping mechanism to try to escape these terrible water circumstances.

2. Improper Water Parameters

Molly fish are susceptible to changes in water temperature and pH levels, and any abrupt changes can be harmful.

For example, a rise in water temperature will leave scars and a painful burning sensation on their bodies.

Also, excessively high pH levels create an overly alkaline environment, causing the fish to develop significant health problems.

The longer they stay in a high alkaline environment, the more their mucus layer (the body’s protective layer) dissolves, exposing them to bacteria and other infections.

As a consequence, they will be stressed and will try to escape by looking for cleaner and safer waters outside the tank.

3. Inappropriate Tank Size

Molly fish are active swimmers that require a lot of room to swim freely. 

So when they are kept in a too-small tank, they feel trapped and uncomfortable.

Also, smaller tanks prevent fish from having enough oxygen in the water column. Thus, your molly fish will start gulping at the top of the tank for oxygen.

In this case, jumping out of the tank may be their way of seeking a larger and more comfortable space.

4. They are Curious

One of the unexpected reasons that molly fish jump out of the tank is that they are curious by nature.

They are attracted to anything new in their environment, including you walking by their tank or any brightly-colored objects.

So, if you notice your molly suddenly swimming erratically towards the top of the tank, there’s a chance they’re trying to jump out to see what’s on the other side.

5. Poor Diet

Mollies are always hungry and will consume anything put in front of them, including leaves, algae, and tiny invertebrates.

When they don’t get enough food, they become malnourished and their health starts deteriorating.

Hence, they will start to believe that there is food outside the tank and will jump out in an attempt to find it.

6. Lack of Oxygen

When the water in their tank is not adequately aerated, molly fish will look for oxygen-rich waters elsewhere.

They will even jump out of the tank desperately trying to get to the surface for a gulp of air.

This lack of oxygenated areas can be caused by food leftovers decomposing and releasing toxins that pollute the water.

Also, it can be caused by too many fish in the tank, which creates competition for oxygen.

How to Stop Molly Fish from Jumping Out of the Tank?

1. Ensure the Tank Has Enough Space

As we mentioned, molly fish jump out of the tank if kept in a small container or in overcrowded situations.

Therefore, you should provide a bigger tank with plenty of space to prevent your fish from jumping. The ideal tank size for molly fish is at least 30 gallons.

2. Maintain Optimum Water Quality

Maintaining high-quality water is essential for their health and will prevent your lovely fish from escaping.

Hence, you should perform regular water changes, at least once a week, to remove toxins and impurities from the water.

However, be careful not to change the water too frequently, as that can be stressful for your fish.

Also, you should add biological filter media with aquarium beneficial bacteria to the filter. 

In no time, these organisms will transform toxic ammonia levels into vital nitrate in the aquarium nitrogen cycle.

Moreover, an aquarium filter will provide a suitable water flow for your molly fish while aerating the water and keeping it clean.

And to acquire high oxygen levels, you can invest in an air pump and an airstone

The air stone will help to circulate and oxygenate the water, making it easier for your molly fish to breathe.

3. Maintain Correct Water Parameters

As said before, molly fish require a healthy environment and are very needy when it comes to water parameters.

Therefore, you should maintain the following limits:

  • Water temperature: 72-78 F
  • pH level: 7.5-8.5
  • Ammonia: 0 ppm
  • Nitrites: 0 ppm
  • Nitrates: less than 20 ppm

To avoid any fluctuations in pH levels, you can use a pH test kit to regularly check the acidity of the water.

If you are not living in tropical climate conditions, you should use an aquarium heater to maintain the water temperature within the desired range.

4. Add Plenty of Rocks & Aquarium Plants

Mollies are shy fish that like to hide when they feel stressed or threatened to avoid aggressive tank mates.

Thus, they need plenty of hiding places in the form of rocks and aquatic plants to feel safe and secure.

Not only will this provide a stress-free environment for your molly fish, but it will also make the tanks more visually appealing.

5. Avoid Overfeeding

Overfeeding will cause waste levels to rise, which can be fatal for your molly fish.

To prevent this, you should only feed your molly fish twice or three times a day and only give them as much food as they can eat in three minutes.

6. Add a Tank Lid

Installing a lid or cover over the top of the tank can help prevent your molly fish from jumping out.

Not to mention, it will also help to keep the water warm and humid as well as stop debris and dust from getting into the tank.

However, you should make sure that the cover is big enough for your hands to fit inside easily. 

So, you can feed your molly fish without having to remove everything from the tank first.

How Do You Catch a Jumping Molly Fish?

If you’ve seen one species jump out of the tank and it’s still in your house, there are a few options for catching them:

  • If you have long-handled nets or butterfly nets, use them
  • Mop up any other molly fish on the floor first, then gather your net and scoop out each one from beneath furniture, etc
  • Use an ice cream container lid and paper to contain the fish, then scoop them up
  • Use a plastic bag with some water in it as bait. Grasp the opening loosely with your hand while wiggling it about. This will attract any fish nearby, making it easy for them to scoop into the container
  • If this fails, remove anything and everything near the fish. Then, if they jump out again, you should be able to catch them more easily


How Long Does Molly Fish Live?

The average lifespan of a molly fish is 2 to 5 years if they are well cared for and have a suitable environment.

What Can I Feed Molly Fish?

You can feed molly fish a variety of foods, such as live food, frozen food, pellets, flakes, and vegetables.

How Big Do Molly Fish Get?

Molly fish can grow up to 4 inches in length.

Do Molly Fish Need a Filter?

Molly fish need a filter to remove toxins and waste from the water as well as aerate the water and keep it circulating.

How Many Molly Fish Can I Put in a Tank?

A general rule of thumb is to have 1 inch of fish per gallon of water. For example, if you have a 10-gallon tank, you can put 2 molly fish in it.

Can I Put Other Type of Livebearers in the Same Tank As Molly Fish?

Compatibility depends on the other species of livebearer you want to house. For instance, keeping guppies, platies, swordtails, and endlers with them is recommended because they are both peaceful fish.

What Fish Are Jumpers?

Some predatory fish can jump out of the tank, such as the oscar, lion head, and weather loach.

Also, other fish that are alternative jumpers include guppies and mollies, dragonfish, gouramis, angelfish, and even saltwater shrimp.

Why Do Molly Fish Jump Out if a Tank Is Too Small?

When the tank is small, it provides little space for molly fish to avoid predators. As a result, they will often jump out of the tank in an attempt to escape.

Also, in small spaces, there are not enough oxygenated areas for them to thrive, so they will often jump out in search of oxygen.

Does My Molly Have Teeth?

Molly fish have a set of pharyngeal teeth that help to grind up food before it enters their digestive system.

Is Molly Hardy Aquarium Fish?

Molly fish are hardy aquarium fish and can live in a wide range of conditions.  However, they are not tolerant of sudden changes in water parameters and prefer stability.

Are Molly Fish Shy?

Molly is usually a shy fish and tends to hide when they are first introduced to a new environment. 

However, once they get acclimated to their surroundings, they will become more active and social.

Do Mollies Sleep?

Mollies do sleep, but they do not have eyelids, so they cannot close their eyes. 

Instead, they rest in a state of semi-consciousness in the water column or at the bottom of the tank.

Last Words

Mollies are a great addition to any aquarium. They are colorful, hardy, and relatively easy to care for.

However, they are also known to be jumpers, so it’s important to take precautions to prevent them from escaping their tank.

Remember to provide them with a spacious tank, plenty of hiding places, and stable water conditions to ensure their health and happiness.

We hope you enjoyed this article and found it helpful. If you have any questions or comments, please feel free to leave them below.

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