How Long Can Fish Live In A Bag – The Quick (and Detailed) Answer

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Are you wondering how long your fish can live in a bag? If so, you’re not alone. While the answer may seem simple enough, there is more to it than meets the eye. In this post, we’ll take a closer look at exactly how long fish can live in a sealed bag and what you can do to make sure they stay healthy during that time. So, whether you’re getting ready to move your fish or just want to know more about the shipping and transporting process, keep reading for everything you need to know!

Transporting Fish

There is no fancy way to transport fish. Whether you’re a hobbyist or distributor, you’ve most likely received a fish, invertebrate, or plant in a plastic bag filled with water. There must be a better way to transport fish, right?

As with anything in the aquarium hobby, stability is key to making the transportation of fish and invertebrates as easy and stress-free as possible. But the truth is that this process has been nearly perfected and largely results in success.

How Long Can Fish Live In A Bag? (The Quick Answer)

Fish in Transport bags

Surprisingly, shipping fish and invertebrates in plastic bags is quite a reliable method that has been used for decades. On average, fish can survive for 6-9 hours in a sealed plastic bag as long as other conditions are met. It is strongly encouraged to only keep fish in a bag for a few hours at most, though.

For overnight shipments from online retailers, fish are prepared to spend at least 24 hours in these conditions by maximizing oxygen and stabilizing temperature. Retailers have perfected these methods so much so that fish can often spend up to a couple of days in transit.

This is in comparison to corals and plants that can withstand even several days or more in a plastic delivery bag when packaged correctly. Unfortunately, other invertebrates do not have such a big window.

Many fish keepers are usually pleasantly surprised that their fish arrive alive even when there has been a delay in delivery. Sometimes though, even an early package can cause dead or damaged fish or invertebrates due to unstable conditions or poor shipment preparation.

Fish Transportation Factors

Hundreds of fish are moved and delivered daily. If they can travel across oceans then your fish can definitely make it home safely from your local pet store. However, it can still be very stressful for freshwater and saltwater fish to make the move from the pet store to the home aquarium.

Here are some of the factors that will affect how your fish does during the trip and just how long you have before you need to release your fish.


Temperature is the biggest problem when it comes to keeping fish alive during transportation. Whether it’s for just a couple of hours or it’s for a several-day delivery, the temperature can cause multiple fish and invertebrates to die during the process.

The problem is that tropical fish don’t stop being tropical just because they need to be transported. Most of these fish species need to be kept at a constant water temperature between 72-82° F. Any deviation from this or out-of-range value can cause the fish to die; it should also be noted that hotter water will hold less oxygen than colder water, which can become problematic in places that experience seasonal changes.

Contrary to popular belief though, tropical fish should be shipped at the lowest temperature possible. A lower temperature will slow down metabolic processes, which helps preserve oxygen and water quality.

The simple fix to varying temperatures is using extended release heat or ice packs. These packs are usually good for a couple of days and will help maintain water temperature as long as the fish bag or box is also properly insulated; it is very common for fish to be transported in styrofoam with plenty of padding.

If you’re transporting fish over a short period of time, then an insulated container, like a cooler, may be used to help stabilize and maintain temperatures. In the colder months, it may be worthwhile using a heat pack for extra insulation or simply running the heat in the car. In the warmer months, air conditioning should help keep the water temperature down.

Some pet stores may even deny shipment if temperatures are extreme because of this.


The second problem when it comes to transporting fish is maintaining oxygen levels. Whenever a freshwater or saltwater fish is put into a sealed container, it has the possibility of suffocating due to decreased levels of oxygen and increased levels of carbon dioxide.

As mentioned before, oxygen is affected by water temperature: warmer water holds less oxygen while cooler water holds more oxygen. Ideally, the plastic bag should remain at tropical temperatures with enough oxygen for the shipment.

Oxygen can be difficult to regulate as fish bags are a closed environment. Oxygen is being used by the fish while carbon dioxide is being released back into the water. With no new source of oxygen, the available oxygen can be depleted. Furthermore, carbon dioxide contributes to forming weak acids in the water which lowers water pH.

No matter how you pack your fish, air will always be limited. However, there are a few ways to ensure that your fish have just enough oxygen to make it through their trip.

  1. Use large bags with fewer fish. A bigger bag means more oxygen, especially if you don’t fill up the bag with as many fish. However, this can be heavy and wasteful, making it difficult to ship.
  2. Test water parameters. This might seem like a simple hack, but knowing the parameters of the aquarium water before sending fish out from it can make the move that much safer and easier. Water quality should be near perfect and fish should be healthy and ready for a stressful few days.
  3. Fill the bag with 1/3 water and 2/3 oxygen. This will give a good balance between water and air for gas exchange. Some hobbyists choose to fill their fish bags with pure oxygen, though this isn’t usually necessary for the average hobbyist or aquarium retailer.

For longer, but not overnight, shipments, some hobbyists may choose to bring a battery-operated air pump with them. This facilitates gas exchange, moving in new oxygen into the water and exporting used carbon dioxide. To make this work efficiently, the system must be open, meaning that new air can be diffused at the surface of the water.


Ammonia can quickly kill fish and invertebrates that are stuck in sealed containers. Ammonia is created as a result of metabolic processes as well as fish waste and can become toxic at relatively low concentrations. In a full aquarium setup, ammonia is usually quickly processed and neutralized by beneficial bacteria.

There is no way to stop ammonia from accumulating in a fish bag entirely. However, there are a few ways to lessen how much of these toxic chemicals enter the water during transport.

The best way to stop ammonia from entering the water is by limiting feeding in the days before the shipment. It is recommended to not feed fish at least 72 hours in advance. This will lead to fewer metabolic processes and decreased levels of ammonia being released; the lowered temperature will also help slow the remaining metabolic processes to lessen ammonia export even more.

Another method for safe shipment is using an ammonia neutralizer. This should detoxify ammonia and nitrite for short periods of time. These products can be difficult to dose correctly and are oftentimes unnecessary.

How To Ship A Fish

Whether you’re sending a freshwater or saltwater fish to another hobbyist or purchasing your first coral online, you might be wondering how the process works. Each hobbyist and fish store has his or her own method, but here is a general breakdown for shipping fish, corals, and plants. The video below by Michael’s Fish Room explains how to ship freshwater fish. We will go further in the paragraphs below.

Shipping Fish

Fish are the most time-sensitive in this process. They need large amounts of oxygen, produce a lot of waste, and can get trapped in the corners of a closed container.

A fish bag can be small, medium, or large. Most fish are packaged in small groups or individually depending on the fish species. These bags are often placed together in an insulated styrofoam container with heating pads. It is important that the fish bags stay upright as fish can get caught in the corners.

Live fish shipping is usually overnight or over 2 days. Any more time than this can become dangerous for the fish.

Shipment Containers

The most popular shipment container for fish is a plastic bag in a foam box. Most hobbyists use ice coolers or other temperature-regulated containers for local pickup.

Some retailers have started using a new technology called a breather bag. These bags are designed to allow gas exchange through a semi-permeable surface; both oxygen and carbon dioxide can freely move in and out of the bag.

Breather Bags

A new way of transporting fish. Allows oxygen and CO2 to move freely. Commercial sellers can purchase Kordon brand bags from their local wholesaler

Buy On Amazon

In most cases, breather bags are not necessary and fish will survive just fine without the extra gas exchange. However, these bags can be good for longer trips and more expensive fish.

It is very common for hobbyists to trade fish, corals, and plants in a ziplock bag. Though ziplock bags are safe enough for fast deliveries, these bags are difficult to fill and don’t provide much leftover room for oxygen. Speaking from experience, they are also very prone to leakage!

Shipping Corals

Believe it or not, corals aren’t as sensitive as fish when it comes to shipping. Corals can live in a bag without light for a couple of days without any damage; they might just take a couple of days to open back up in the new tank.

Pet stores like to use plastic containers, like urine cups, as a way to hold the frag in place for shipping corals. This greatly reduces the likelihood of the coral rolling around in the container, potentially causing damage; soft corals, like zoanthids, are regularly shipped in a regular plastic bag. A great example of a seller shipping corals is FishOfHex. I’ve known him over the years. Travis is one of the good and honest sellers in the industry. Give him a shot if you are looking for quality frags.

While corals aren’t likely to die due to lack of oxygen or high levels of ammonia, they are very sensitive to changes in temperature. Because of this, fish stores monitor the weather very closely and provide plenty of insulation.

Most corals are shipped overnight, though they can safely be transported over the course of 2-3 days.

Shipping Plants

Shipping plants is the easiest process, though freshwater species are still slightly sensitive to extreme temperatures.

Plants can survive in closed containers for longer than is needed for a successful trip. A plant cutting is placed into a plastic bag and given some water, usually through an absorptive sponge around the roots; there is no need to keep the plant submerged in water for transport. Little additional packaging is needed, though a heat or ice pack is added depending on the climate.

Plants can be successfully shipped over the course of 4-7 days. Of course, it is better to receive the plants as soon as possible, but hardier species can definitely live much longer than this without any problems.

How To Acclimate A Shipped Fish

Once your fish arrives, you need to know how to make the transfer to your tank seamless. Acclimating new fish that have been stressed for a few days is a little more involved than simply taking a fish home from the pet store. This is because of ammonia.

When fish are shipped, pH drops due to carbon dioxide entering the system. Eventually, ammonia becomes a less toxic form, called ammonium, at a certain pH level. Fish are able to live in these ammonium conditions longer than they are in water with high concentrations of ammonia.

However, once the bag is opened upon delivery, the carbon dioxide is allowed to escape and the pH rises again, and ammonia quickly spikes. In these moments, the fish can be killed!

For a long time, it was believed that letting fish slowly drip acclimate to the tank water for several hours was the best acclimation practice. We now understand that it’s best to get these shipped fish into the tank immediately. Don’t forget that shipped fish can also carry diseases and should not be placed directly into the main aquarium upon arrival!

Instead, the bag should be floated at the surface of the aquarium water until temperatures match. The fish may then be placed into a quarantine system for at least 2 weeks to observe for signs of illness. Make sure that none of the water that came in the bag enters your aquarium’s system.

Shipped corals may be temperature acclimated, dipped to remove pests, and then added immediately to the aquarium. It’s best to place coral frags on the substrate or on a frag rack in order to monitor health and to understand the coral’s preferences for lighting and flow in the aquarium. Some hobbyists do prefer to quarantine corals. I’m a fan of QT’ing corals, but I know most hobbyists aren’t.

Plants may also be added directly to the aquarium once treated for pests. If you purchase a tissue culture plant, they are disease and pest free. Tissue culture are the best plants to buy for peace of mind.

Many online fish retailers have a dead on arrival (DOA) guarantee which states that aquatic pets that arrive near death or are already dead can be returned for store credit or a full refund. A time limit is often given for this window and the container must be unopened. The DOA may be denied if the weather did not allow for safe delivery, though every retailer is different.

Final Thoughts

The past few years have caused many hobbyists to turn to online stores for saltwater and freshwater fish, corals, and plants. Online stores usually have a bigger selection and lower prices, but the thought of sending something live in the mail can make some hobbyists nervous.

Luckily, with the right packaging and timely delivery, fish survive being shipped just fine.

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