Acclimation

Now that you have received a box of carefully packed fish via UPS or you’ve retrieved them from the airport, there are some important steps to follow which will ensure the fishes successful introduction into your tank(s).

Keeping the lights off on your tank during acclimation and for a couple hours post- introduction of new fish will reduce stress.  The fish inside the box will have been in total darkness anywhere from between 15-25 hours.  Immediate exposure to bright lights can shock them.

Floating the unopened bag in an unlit tank for 10 minutes will ensure that the water temperature inside the bag is equal to that in your tank.

You may then open the bag and add aquarium water of approximately about 1/2 to 2/3 the volume of shipping water.

For small and medium-sized fish of approximately 1-3 inches length or for bags containing a few smaller fish (1-2.5 inches), you can hang the bag over the side of the tank now.

For larger sized fish of > 3.5-5 inches length or for bags containing multiple medium-sized fish (approx. 3-4 inches), the results of hanging the bag over the side of the tank can cause severe oxygen depletion of the water inside the fishes bag in a short time.

In this case, try and catch air in the bag and re-tie the rubber band around the bag to imitate as best you can the appearance of the bag upon receipt.

Laying the bag down horizontally will ensure that maximum surface area of water is exposed to air exchange during this time.


For most of the cichlids, catfish, barbs and tetras that I offer, after another 10 minutes, under normal circumstances, the fish are ready to be introduced into their new home.

It’s not advisable to add shipping water into your tank as it’s often visibly polluted with fish wastes and may be discolored from the breaking down of wastes that occur while the fish is in transit.

Either netting the fish from the bag or pouring the fish into a net placed over a bucket will allow you to avoid adding shipping water into your aquarium.

While the newly added fish are transitioning to their new environment, you may take this opportunity to feed the current residents of the tank something that they really enjoy to eat.  While the ‘home court fish’ are busy feeding, their attention will be diverted from the new arrivals that are probably overcoming shipping stress and learning their way around their new home.


The method known as ‘drip acclimation’ can be more stressful than helpful for many fish and often inadequate to accomplish the act of water temperature equalization.

While there are advantages to using this method on certain fish with proper precautions taken, the vast majority of fish I offer, coupled with the average packing density, do not favor using the drip method.

Reason #1 to not drip the fish: The tendency for this water to be cooled by ambient air temperature (room temperature in your home) outside the heated aquarium will prevent temperature of water in the bag (or bucket if you’ve transferred fish from shipping bag to other receptacle for acclimation) from reaching that of the tank by merely dripping aquarium water into a bag.

Reason #2:  Only a relatively small amount of water is used during transit.   I generally ship fish using about 1/3 the volume of bag with water and 2/3 the volume of the bag containing pure oxygen pumped into bag upon packing.  There is enough water to provide safe transit of the fish and keep water weight inside box at a reasonable level.

Once the bag is opened and the 100% oxygen they were shipped with  is taken off the fish, the clock spins extremely fast towards oxygen depletion in that small amount of shipping water.  As mentioned previously, this is used up most quickly by a large fish or by multiple fish in a small amount of water.  If aeration is not provided by an air pump to the acclimating fish, the fish are in serious danger of oxygen starvation.

Reason #3:  Drip acclimation can cause a reaction in the shipping water by which the wastes produced by fish while in transit may be fueled to reach toxic levels upon introduction of aquarium water.

In the event that a bag containing fish arrives deflated and severely lacking of water via puncture of bags by fish spines (a common occurrence when shipping larger cichlids and catfish), the fish should be introduced immediately to tank.  It’s a much better solution to getting fish into a preferred environment versus an unfavorable environment such as that of a leaked-out bag.


Larger fish invariably take longer to transition to a new environment than smaller fish.

Some species will proceed to lay down upon being released into a new tank.  Examples of this behavior may be witnessed upon receipt of many round-bodied South American cichlids such as oscars, chocolate cichlids, severums, festivums, Uaru, discus, angelfish, and frequently adult cichlids of varied origins.

This behavior is expected and seems to be the rule rather than the exception.  Ensure that new fish are not picked on by current aquarium inhabitants while they ‘come around’ or ‘transition’ in their own time.  This may take anywhere from an hour or two to overnight.

Please also keep the aquarium lights off as long as any fish are still in this transition state.

While smaller/younger fish may begin feeding almost immediately post introduction to your tank, larger species may take a day or so before they are comfortable to resume feeding.

If you have any questions at all regarding immediate or long term care of the fish I have shipped you, please do not hesitate to call or email with questions.

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