by Norm Ruebsamen


Fish and hobbyists can both ‘breath easier’ with the advent of breathable bags. These bags really do allow oxygen to permeate the plastic.  Not only do they let good air in, but they let the bad air out. According to the Kordon website: Carbon dioxide exits the bags at 4 times the rate oxygen enters the bags, thereby constantly purging the water of toxic carbon dioxide, and allowing oxygen to replace it in the water. Breathable bags function well when packed in conventional styrofoam or corrugated boxes. Foam and cardboard boxes have a high rate of breathability, even if these containers are sealed with tape. Air is normally over 20% oxygen, which is over 200,000 ppm (parts per million). Fish normally have only about 4-14 ppm oxygen available to them in water. It takes only a small amount of air passing through the packaging materials to sufficiently oxygenate the water in breathable bags.


Standard fish bags made of polyethylene have no mechanism to allow the passage of gasses through the bag wall. When using these “barrier” bags, oxygen must be added to the bag prior to sealing. Once the supplied oxygen is used up there is no more available. Toxic carbon dioxide builds up in the water, displacing the oxygen. 


There are many other advantages to using breathable bags. Because it is not necessary to add a large amount of air to the bag they take up less room in the box when shipping. Also, no air means no “sloshing” sound to alert postal workers. In addition, breathable bags are reusable with proper care.



I bag fish individually, one fish per bag, and then tie both bags together with a rubberband. With standard fish bags, one would put the fish in a small amount of water and a lot of air. With a breathable bag you want to fill it full of water leaving just enough room to tie it. Seal the bag with as little airspace as possible. Fish adapt readily to the lack of an airspace and it is not needed. It is best if there is no air pocket in the bag so that there is no water movement, keeping the fishes calmer. 


Breathable bags can be sealed using any of the current methods: rubber bands, twist ties, knots, etc. If you are dealing with a large volume of fish a bar type heat sealer is an excellent way for fast efficient sealing. These bags are more difficult to label so you must be sure that your label is waterproof (can be attached to the top with a rubberband). Breathable bags should not be shipped inside a larger liner bag. The barrier effect of the outer bag would prevent the breathable bags from doing there thing.



Wrap each bag loosely in newspaper. The newspaper allows the bag to “breathe” and also absorbs leakage. These bags tend to “sweat” during shipping.  And as you know, if any moisture comes through the box, it will more than likely be confiscated. When packing my shipping container I wrap each bag in newspaper and then separate them with loosely packed peanuts or flat pieces of corrugated cardboard or layers of newspaper, so that as much bag surface area as possible is exposed to the air in the shipping container.



Don’t be afraid to acquire killies from people in other countries.  With the use of the internet you can make contact with hobbyists all over the world and bring in species that are new to our area. 


The number one rule is: Don’t be greedy. Don’t try to bring in 15 - 20 pairs of fish.  Simply find a species you really want and try for 2 - 3 pair.  You will find that the smaller shipping box will draw much less attention when going through customs. If your mailman can stamp ‘small packet’ on your box, its in the right size range.


Breathable bags allow for the use of much smaller boxes. I always use a styro with an unmarked outer cardboard carton. Styros are too suspect and draw unwanted attention when traveling in and out of the US.


One other point, if you are receiving fish from abroad and your contact does not have access to breathable bags, its a great idea to mail him some bags in which to ship your fish. Your fish will arrive much healthier and in better condition and losses will be minimized.



Do not float breathable bags in your aquariums. The bag will no longer breath when immersed in water and the fish may actually suffocate. Also as the temperature inside the bag rises so does the ammonia level. Ammonia levels of just .02 ppm could harm or even kill your new fish. It is better to gently pour fish and water to a plastic container.  Slowly add aquarium water to acclimate the fish. When the fish are acclimated to the water and temperature of their new tank, net the fish and transfer them to the aquarium.  Discard acclimating water. Never add shipping or acclimating water to your tanks. You could be adding contaminants and unwanted guests. Keep fish in the dark until they get accustomed to their new surroundings.  Don’t worry about feeding your new fish for at least 3 hours.