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How Long Can Fish Live In a Bag? Vet-Approved Facts & Care Tips

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By Lindsey Stanton

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Dr. Luqman Javed

DVM (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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When you buy a new fish from the pet store, it likely comes home with you in a bag. You know you have to give the fish time to acclimate to the new tank environment. However, you might not know how long the fish can safely be kept in the bag.

The short answer is a fish can live in a bag for between 7 and 9 hours. Fish may last longer in bags that contain additional chemicals for absorbing fish waste and ammonia. However, there are many factors that influence the amount of time fish will be safe and comfortable in a plastic bag. Read on to learn more.

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Factors That Impact How Long Fish Can Live In a Bag

While fish can generally be safely kept in a plastic bag for 7 to 9 hours, this amount of time is not always healthy. It’s also possible a fish can survive in a bag for longer than 9 hours if certain conditions exist.

  • Oxygen – Fish need oxygen to breathe. In a tank, the filtration system helps move the water around. Fish absorb the oxygen from the water as it moves over their gills. When you keep a fish in a bag for too long, the oxygen levels will deplete and the fish will suffocate.
  • Air vs. pure oxygen – If the bag is filled with pure oxygen instead of air, the fish can survive longer. Most pet stores used oxygen to fill fish bags instead of air. Using pure oxygen will make it possible for your fish to breathe more easily in the bag.
  • Number of fish in the bag – If you’re bringing home multiple fish at the same time, you’ll want to either ask the pet store to put them in separate bags or remove them from their bags sooner. The more fish you have in a bag, the more quickly the oxygen will be depleted.
  • Size of the bag – The bigger the bag, the more oxygen you can put in it. Only about one-third of the bag should be filled with water. The rest should be filled with oxygen.
  • Type of bag – Ziplock bags don’t make good choices for fish transport. They can break too easily. Hard plastic containers are also not ideal. They don’t allow for enough oxygen nor can you use them to acclimate your fish to the new tank like you can a plastic bag. This is why polybags are typically used for fish transport. They are thicker than Ziplock bags, so there’s a lower risk of ripping. They can also be topped with plenty of pure oxygen to keep your fish safe.
  • Transportation conditions – Factors such as temperature can impact the rate at which the oxygen is used up by your fish. If it is too hot or cold, the fish can become agitated or excited. This will cause them to use the oxygen more quickly than if they were calm and comfortable. A small cooler is a good way to transport fish home. If you place the bags in the cooler, the temperature won’t fluctuate and the bags won’t bounce around.
  • Additives – The water in some bags is supplemented with chemicals or additives that help absorb fish waste (such as ammonia) to make the water safe for the fish for as long as possible.
  • Last meal of the fish – If the fish wasn’t fed for a day or two before being placed in their bag, they will produce less waste. Therefore, they may last longer in the bag.
goldfish in plastic bag
Image Credit: TRAN THI HAI YEN, Shutterstock

Acclimating New Fish to Your Tank

Another thing you need to consider when bringing a new fish home is how long they need to acclimate to your tank. You need to let the bag float in the tank for 15 to 20 minutes so the fish can acclimate to the temperature.

You also need to allow your fish to adapt to the pH levels in the new tank. This is done by adding a little of the tank water to the bag with the fish in it. You should do this several times over an hour or two. Please note that if you already have fish in the tank at home, you should place your new fish in a quarantine tank instead of your existing one.

Once the fish has had a chance to acclimate, you’ll want to add them to the tank using a net. Don’t add the bag water to the tank. It can contain bacteria and diseases that might harm your other fish.

You’ll need to add these steps into your calculation of how long your new fish will be in a bag.

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Final Thoughts

While some fish can live for up to 48 hours in a bag, if the oxygen levels are high enough, most cannot survive for more than 7 to 9 hours. You’ll need to be mindful of this when you bring new fish home. Accounting for how long it will take to acclimate them and the levels of oxygen in the bag is essential for a healthy introduction for your fish.

Featured Image Credit: kao, Shutterstock

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