How Long Can Fish Stay In Bag? The Real Answer!

Jul 22, 2022

How Long Can Fish Stay In Bag?

Image Credit: Hairyeggg (CC License)

Every time I bring home a fish from the store, it feels like I’m in a race against time. I feel claustrophobic just looking at the poor fish cramped in a tiny transparent bag filled halfway with water.

The fish barely has space to move around. The chances of the fish suffocating increase dramatically. One small mistake and the fish would be as dead as a doornail. 

So, how long can fish stay in a bag? What happens when the fish is in the bag? Are there any tricks you can pull to make their detention any easier?

Keep reading to know. 

How Long Can Fish Stay In Bag?

There’s no rule set in stone that determines how long the fish can stay in a bag. It depends on several variables like the fish species, the size of the bag, and temperature. Having said that, a healthy fish can live in a bag for at least 7-9 hours on average. 

If the living conditions within the bag are good, the fish can even live for 48-72 hours. So that’s 2-3 days. 

Most of the time, the bags that fish are shipped in from breeder to wholesaler and from wholesaler to the pet store are inflated with oxygen. In general, there’s a ratio of ⅔ oxygen to ⅓ water. 

Therefore, fish packed in this way have a higher chance of surviving.

Also, transhippers will open and repack fish if required when they pass through their facilities. 

However, when you’re buying fish from your LFS, chances are that the extra oxygen is not added unless you specifically request them to. In this case, the fish will survive in the bag for just a couple of hours. 

Excess air must be removed and replaced with pure oxygen. Likewise, the bag should be properly sealed and placed in an insulated container, which in turn is placed in a cardboard shipping box. 

Can Fish Survive In A Bag Overnight?

Yes, a fish can survive in a bag overnight if the right living conditions are met. The bag in question should be big enough, have an ample amount of oxygen, and be kept at the right temperature. 

When making the long journey from the breeder’s to a store, a fish often has to stay overnight in a bag on many occasions. 

And naturally, the concerned parties know what they’re dealing with and make necessary arrangements. They ensure the right oxygenation, temperature, and water levels are maintained in the tank. 

How Long Can Fish Survive Shipping?

Well-packaged fish can survive in a plastic bag for 2-3 days without any problem. Once again, the right oxygenation, temperature, and water levels should be maintained. 

The water will get dirtier and warmer/colder during shipping, but the fish will have adapted gradually. The fish’s metabolism would also be decreased significantly. 

As I said in the beginning, several factors come into play when ascertaining how long the fish can stay in the bag. 

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Credit: VasenkaPhotography (CC License)

Can you imagine what it feels like to be forcibly taken out of your home, packaged in a plastic bag, tossed in a dark cardboard box, and made to travel hundreds of miles in the back of a lorry?

Sounds stressful, isn’t it? Well, that is exactly how your fish feel too. 

Fish don’t like moving. Needless to say, they find it highly stressful. And when stressed, fish use up more oxygen. Well, that’s how our bodies work. 

The blood pressure and heart rate increase. So, breathing helps to control the nervous system and encourages the body to relax. 

The best bet here would be to use a concentrated source of oxygen and supply enough to last the entire journey. The bag should at least contain half its total volume of oxygen. 

The general practice is to seal the bag with at least two-thirds oxygen. The compressed cylinders of oxygen can be rented or bought from commercial sources. 

Dead Fish Also Use Up Oxygen Present In The Bag

The sudden death of any fish in the plastic bag will rapidly decline dissolved oxygen level as bacteria works to decompose the dead fish. 

Therefore, it’s best to pack the fish individually. This sounds painstaking, but it drastically increases the survival chance of each fish being shipped. 

Temperature May Fluctuate 

This point sounds so obvious, but I had to include it. It’s only natural that the plastic bag will endure different temperatures at different times. 

And if fish are sensitive to one thing, it is temperature. If it’s too hot, there’s a problem. If it’s too cold, there’s a problem. 

Needless to say, fish are cold-blooded animals. They cannot regulate their body temperature as we do. So, they will be at the same temperature as the water they are in. 

All fish species have an ideal temperature range in which they thrive. 

Naturally, they also have at which they can just survive. 

The fish will become stressed when the water deviates from the ideal range. Also, the fish’s metabolism is directly proportional to the water’s temperature. 

Therefore, once the fish is in the plastic bag, place the bag in an insulated container. A container like this helps to maintain the initial temperature. 

It’s recommended to ship the fish at the lowest optimal temperature so that their metabolism is slowed down – this will drop the rate at which the rest of the environmental factors worsen inside the box. 

Don’t Use Ziplock Bags 

Ziplock bags are lined with chemicals that may seep into the water and make the water toxic for fish. Opt for a good-quality polythene bag. 

To make matters worse, ziplock bags can collapse quite easily and leak oxygen and water – nullifying the chances of your fish making it alive. 

Also, ziplock bags are pretty narrow. The bag should ideally be large and round to ensure enough space for safety. 

All in all, ziplock bags aren’t the right choice of material for shipping fish. Instead, you should use a 4-mil plastic bag. Shippers double- or even triple-bag the fish to ensure that at least one bag remains watertight. 

Fast The Fish

Fish excrete ammonia across the gill membrane to get rid of nitrogenous waste. And you already know how toxic ammonia is to little fish. 

To decrease the bag’s ammonia level, you must withhold food from the fish for at least 24 hours before shipment. It will reduce their metabolism and the amount of waste they’ll discharge into the water. 

Final Words: How Long Can Fish Stay In Bag?

There’s no one specific answer to this question. Depending on how the fish has been packed, it can live for just a couple of hours or survive 2-3 days. 

Using reliable and durable plastic bags, getting the oxygen level right, and shipping them in an insulated box lessens the chances of any hazard during travel. 

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rohit gurung author at urbanfishkeeping

About Rohit Gurung

My never-ending love and fascination with Aquascaping started when I received a red-eared turtle for my 10th birthday.

Apart from researching and writing, I spend hours gazing at my 3 turtles. And yeah, I bask alongside them too.