Jonah's Aquarium

Acclimating Your New Fishes

If your fish were packed in Breathing Bags, do not float the bags in your aquarium or pond! The Breathing Bags cannot breath in water, only in air. If you have Breathing Bags, there will be no air in the bags and they will have writing on them that says they are Breathing Bags. Non-breathing bags will have air in them that the fish are using to get oxygen. Follow the breathing or non-breathing instructions as needed for your shipment:

Acclimating Your New Fishes

To prevent losses due to changing water conditions, it is necessary to carefully acclimate your new fishes to their new tanks. The following instructions apply to fish that have been shipped to you:

After opening the shipping box, you should use a thermometer to check the temperature of the water in the fish bags. This can be done by placing a thermometer under a bag so the water lays over the thermometer's sensor. If the temperature in the bags is different from that in the new tank by more than three degrees Fahrenheit, you should use the Large Temp Difference Method to acclimate the fish. If the temperature difference is less than three degrees Fahrenheit, use the Small Temp Difference Method to acclimate the fish. Both methods are described below:

Large Temp Difference Method for Breathing Bags and non- breathing bags

If the temperature in the bags is different from that in the new tank by more than three degrees Fahrenheit, prepare a bucket of clean water that is at the same temperature as that in the fish bags. Add water conditioner/chlorine remover as necessary to make the water safe for fish. Remove the fish from the bags and place them into the water in the bucket. You may need more than one bucket if the fishes are incompatible or there are too many for one bucket. You may also need to use an airstone or other aerator to be sure there is sufficient oxygen in the water. Allow the fish in the bucket to slowly warm or cool to room temperature. Check the temperature with a thermometer periodically. This may take several hours or even overnight. The clean water in the bucket will be adequate to keep the fishes healthy. If they show signs of stress, change some of the water with chlorine-free water of the same temperature. Also, keep the bucket covered so that the fish cannot jump out. A towel, plastic bucket lid or plastic wrap will work for a cover. An air stone will speed the warming or cooling of the water by pumping room air through it. Once the water in the bucket has reached room temperature, proceed to acclimate the fish using the Small Temp Difference Method described below:

Small Temp Difference Method for Breathing Bags

Do not float the Breathing Bags in the aquarium or pond. The fish will not have sufficient oxygen if the Breathing Bags are floated. Open the bags and pour out 1/3 of the water into a clean bucket. You may use an aquarium net to prevent the fish from falling out of the bag. Replace the water removed from the bag with water from your aquarium or pond. After five minutes, repeat the 1/3 volume replacement procedure. After another five minutes, replace 1/3 of the volume again. Finally, after waiting five more minutes, the fishes can be moved from the bags to the aquarium or pond.

Small Temp Difference Method for non- breathing bags

Place the fish in their plastic bags in the aquarium where they will reside. Allow the bags to float in the tank for about 15 minutes. If the fish appear distressed, open the bags and roll down the top of the bags so that they are open and floating at the surface. A small portion of tank water may be added to the bags. After 15 minutes, the fish can be released into the aquarium.
If other fish in the tank attack the new fish, try feeding the fish, doing a water change on the tank, or rearranging the decorations in the tank. This will distract the fish and give the new residents time to get their bearings.

If you need any additional help with acclimating your new fish, just ask. Email us at


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