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How Long Can Fish Live In A Bag?

A lot of people dream of having their own aquarium, filled with lots of colorful and playful fish, decorated with the best ornaments and illuminated in fancy lights.

But to achieve this aesthetically pleasing dream, there are a lot of steps that the aspiring fish owner has to go through. For example, you need to do a lot of research on fish care and treatment, get your tank set up and ensure that your water is probably cycled to create a healthy environment for the tank’s inhabitants.

Once you’ve done that comes the all-important step of introducing your fish to the environment. It is crucial that this step is managed carefully to ensure your fish is as stress free and comfortable as possible in their new home.

The step of purchasing and transporting your fish to its new home is a somewhat worrying process for many inexperienced fish owners. Usually this will involve your fish spending some amount of time in a temporary enclosure or bag.

Many people get worried about this stage, asking questions like; how long can fish live in a bag’ and; how can I make sure they stay happy and healthy?’.

In this comprehensive article we address all these questions and more.

How Long Can Fish Live In A Bag?

The essential answer to this question depends on a lot of different factors. For example, not all fish are created equal, this means that different species will have a different resiliency to changing chemistry, close confinement and potential lack of oxygen.

Some species are just naturally hardier than others with regards to these crucial factors, while others may suffer long-lasting damage.

Some fish need a lot of space and dissolved oxygen, so they will obviously suffer more if kept in a bag for long periods.

Also, the size of the fish should also be considered carefully. It is definitely not advised to keep more than one fish in a bag at a time.

Also, not all bags are even created equal. Some temporary bags may permit oxygen to be exchanged with the environment while others will not. This could be the deciding factor when it comes to assessing long can a fish live in a bag.

With all these variables it can be hard to give a definitive answer, but in the coming sections we will explore how fish are affected by being kept in bags. Of course, if you have a specific query relating to your breed of fish, then you should consult an expert for individual guidance. For most common aquarium species though, the following general advice should suffice.

General Rule Of Thumb

With all the caveats given above, there is a simple rule of thumb that you can follow. In a standard bag that you buy a fish in from a pet store, there is enough air in the bag that the fish can survive for between 7 and 9 hours. However, in most pet stores they will specifically add oxygen to the bag before they let you leave the store. This can greatly increase the length of time that the newly purchased fish can survive.

In this case, without outside interference, your precious purchase can survive for up to 48 hours in the bag. This should be more than enough time for you to get home, with your tank already set up, clean and properly cycled.

Thus, you should have no problem in introducing your new fish to its aquatic home. This is for a standard bag of water, which contains between 1.5 and 2 gallons. This is more than adequate for most small young fish or fingerlings. For larger species or rarer breeds, it may be advisable to invest in a more sophisticated solution such as a transport tank.

There Are Differences Between Bags


Video: “Breathing Bags Test (Transporting Fish Long-Distance)”

To the uninitiated you may think that all plastic bags are created equal, and that all should be capable of transporting fish and water.

Well this is not true.

There are a number of requirements for criteria that the plastic bag should possess if it is to be up to the task at hand.

First of all, obviously the plastic should be waterproof. It should be strong enough to not be damaged by transport or the fish thrashing about in the water. Also, when sealed it needs to be airtight. This is important so that the oxygen that is forced into the bag in the pet store does not diffuse and leak out to the environment. This is possibly the most important deciding factor.

Polythene Bags

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There are a number of different types of plastic bags which are suitable for the important job. However, the most common plastic used by pet stores all over the world is polythene. This should be at least 3 mm thick to fully block the outward passage of that all import oxygen.

The chosen plastic bag should be properly rated for the job, because some types of plastic can leach harmful chemicals into the water. This can cause long term damage to the health of your fish, even if they only spend a few hours in the bag.

Ziploc Bags

Many people wonder if they can use ordinary Ziploc bags to carry their fish around. This is not advised for a few different reasons. Firstly, even when a Ziploc bag is closed, there is not a perfect airtight seal.

This will allow oxygen to leak out at an accelerated rate. This can quickly result in depleted levels of dissolved oxygen in the water. Leaving the bag upside down increases the chances of opening this airtight seal. Zippers on Ziploc bags are even known to fail totally, which could lead to a catastrophic loss of oxygen from the water.

For this reason, fish should be kept in Ziploc bags for no more than half an hour. This means they are only suitable for short trips to and from the pet store, not for longer road-trips.

Why Is Oxygen So Important?

The concept of dissolved oxygen is central to the question of how long can fish live in a bag. This is because fish, like humans, require molecular oxygen for respiration. We take in oxygen through our lungs and using our bloodstream it is transported to all the cell of our bodies.

But fish have a very different system. They must survive on the oxygen that is trapped in water. They take this into their body through their gills. But levels of oxygen in the water are much lower than in air.

There is only a few ppm (parts per million) of oxygen in room temperature water, compared to about 200,000 ppm of oxygen in air. And in the enclosed confines of a small bag, unfortunately fish can use up this oxygen very quickly.

This is why pet stores will inflate the bag with pure oxygen before you leave the store. This pressure forces more of that precious oxygen into the water.

Of course, dissolved oxygen is not only an important consideration during transport, it remains important throughout their time in the tank. You must ensure there is a constant high level of dissolved oxygen in your tank.

You can increase oxygen levels by installing aquatic plants, adding aerators, or increasing the circulation in your tank. Some things which may lower levels of dissolved oxygen in your tank would be algae blooms or overstocking your tank with fish.

Other Factors

There are a few things that can really affect how long can fish live in a bag without consequences. The biggest factor is the rate of oxygen consummation. This is directly related to how stresses and active your fish is.

A very frightened or agitated fish is likely to use up a lot of energy in thrashing about and circulating in the bag. Unfortunately, this will just create a bigger demand for oxygen and lead to faster oxygen depletion.

It is best to try and keep your fish calm when you are transporting it in a bag. Avoid sudden jerky movements or loud noises or flashing lights. Having multiple fish in a very small space is the perfect way to make them agitated and distresses, so you should avoid this at all costs.

A fish’s demand for oxygen also depends on the temperature. In warmer ambient temperatures, a fish’s metabolism will be higher, which will cause them to draw more oxygen from the water. If possible, try and transport your fish in cool temperatures, during relative periods of dormancy.

If you are purchasing saltwater fish, then obviously you need to transport them in saline waters. Saltwater fish may be more sensitive to chemicals leaking from the bag, so this could have a detrimental effect on their health.

How To Improve Your Fish’s Time In A Bag

Let’s be honest, bags are just a necessary evil when it comes to keeping fish. They are a convenient and practical solution when you need to transport a fish, but they cannot compare to well maintained and cared for tank. But that’s no reason to not put a little bit of effort into improving the quality of life of your fish for the short period it must spend in the bag.

Following these few tips and tricks should help you to do just that.

  • You should make sure that the water in the bag is clean. Good quality water can be the difference between a healthy and unhealthy fish. This means your water should be free of any visible dirt or debris, but it is equally important to get the water chemistry correct.
  • This means you should also make sure the pH (which is a measure of the acidity or alkalinity of the water) is correct. Also, the level of substances such as ammonia and nitrites should be kept low. Fish will naturally produce these kinds of nitrogenous wastes, and they can be toxic if their concentration becomes too high. It is therefore important they the level is virtually zero when your fish starts its journey.
  • You may need to add a pH buffer to the bag to regulate the acidity of the water and preventing it from dropping too rapidly during the journey.
  • As we have already mentioned, temperature is absolutely crucial. To maintain the temperature of the water at the correct level, it may be necessary to use heat or cold packs. These can be simple chemical packs that help to regulate the temperature of the environment.
  • Equally, for longer journeys, you should consider using insulated packaging to help prevent the water temperature rising to an unsuitable level. Place the bag in a shaded area when transporting the fish. If you follow all these simple tips, then you should avoid any transport disasters.

Moving Your Fish From Bag To Tank

Video: “How to Properly Acclimate New Fish”

This is perhaps the most crucial step. It is important that you recognize that the water in your tank may be very different from the water in the bag, so your fish will need time to adjust.

Some specious are very sensitive to even slight differences in water pH or chemical balance. The best technique to use is a gradual approach.

First let the bag float unopened in your tank for some time. This allows the fish to adjust to its new surroundings. Then open the bag and scoop some water from the tank into the bag.

Over the next hour repeat this process, thus the fish will get used to the tank water. Eventually the bag should sink under the weight and the fish can swim free in its new surroundings.


In this article we have thoroughly answered the question, ‘how long can fish live in a bag’. We have shown that without excess oxygen in the bag, the fish will only be able to survive a few hours. Using the procedure that most pet stores use, of injecting oxygen, the fish should be able to survive for up to 2 days.

There are many ways you can help to increase this time limit and improve the experience for your fish.

This includes using clean water, keeping their stress levels low and introducing them to their new environment in a slow, controlled manner.

Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

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