Most freshwater and saltwater fish losses by wholesalers, retailers, and tropical fish keeping enthusiasts can correctly be attributed to improperly  unpackaging them upon arrival at their destinations.

After purchasing your fish online or from your local tropical fish keeping facility, it is imperative that you acclimate them as soon as possible.

The following explains the water chemistry encountered with fish transport:

As fish breathe, they produce carbon dioxide in their shipping containers.   When shipped long distances, the carbon dioxide is dissolved in the shipping water creating an acidic condition that lowers the pH in the shipping container.

Fish wastes created during transport break down into ammonia that is present in the water as either NH3, NH4+, or a combination of both.   Although NH3 and NH4+ are both toxic to fish, NH3 is the most detrimental.     During extended shipments as the pH is lowered, the amount of NH3 is reduced and the amount of less damaging NH4+ increases; basically making the ammonia non toxic to the fish.

Essentially, the carbon dioxide in the shipping container acts as a tranquilizer to the fish, which is why specimens can be shipped from India, Bali, New Guinea, and other far away locations in closed containers.

Once the shipping bag is opened and the water is exposed to the outside air, the carbon dioxide in the bag escapes and the pH of the water immediately begins to rise, making the ammonia deadly to the fish.


After your fish is brought home, immediately place the shipping container into your tank, preferably an isolation tank, and allow it to float for at least 20 minutes to bring the water temperature in the container to the temperature of the tank water.

Open the shipping container and slowly pour the contents of the shipping container through a net into a waste bucket and release the fish into the isolation tank.

When a large number of fish are being received in a large box shipping container, drain most of the container water off and net out a couple of specimens at a time.   Don’t try to net all the fish at once or you can damage the fish when they are forced together in the net.

With large specimens, Plecostomus, or catfish, wet your hands and place them into the isolation tank by hand.

Sometimes after extended periods in the shipping container, fish may appear to be dead or are barely breathing.   This common “possum like” behavior is due to stress from shipping and handling.

Turn off all lighting in the isolation tank and let the fish alone until they revive.   Do not feed the fish during this stage.

BE PATIENT. It can sometimes take several days for fish to revive from the stress of a long shipment and even longer for them to regain their color.

Change 30 to 40% of the water in the isolation tank daily for the first week, and every other day for the second week.  If the fish show no sign of disease or stress after the second week in isolation, you can confidently move them to their permanent tank.

Sometimes even when you do everything right, your fish will not survive transport.

Before you give up and call in a D.O.A., check the fish’s gills for several minutes to make sure it is still not breathing.    Several species of saltwater fish frequently lay on their sides for several hours to a couple of days before “coming to”.

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