Breathable bags?

[apistomaster]

Kordon's breatheable bags are a very controversial topic in many forums. Like all technology there are pros and cons.
They are not good for spiney fish or very large fish(no large breatheable bags).
The fact is that when used properly they will keep fish alive far longer than conventional bags. It only takes minimal separation with newspaper or WHY to assure good gas exchange. I have seen fish lost in shipment for over a week arrive alive. That doesn't happen with conventional bags.
As far as widespread commercial use for box lots the cost of the nonexistent large bag would be a corner cut by the industry relying on overnight or less air transport but for hobbyists they are a boon. AKA members have widely embraced their use because small fish separately packed to prevent fight damage is the rule. USPS is the most common carrier used and delays seem to be the rule no matter what type of shipping one elects to pay for. It is true that many shippers of small shrimp have adopted them and I have recieved several delayed shipments without any losses. Standard bags quickly become foul.
Adding substances such as Amquel is discouraged as they consume dissolved oxygen which outweighs the risk of ammonia build up which takes longer to occur. Besides the pH of the shipping water drops reducing the toxicity of the ammonia considerably adding more safety factor than additives.

 

[Kathy55g]

If CO2 is exchanged with the air outside the bag, why would pH drop?

 

[apistomaster]

Hi Kathy,
The CO2 molecules are larger than the O2 molecules and the bags are a semipermeable membrane which allows the O2 to pass more freely than the CO2. The fish inside is contantly respirating CO2 so the gradient of outside CO2 vs inside is such that CO2 bulids up faster than it is exchanged with the outside. The result is that CO2 is preferentially retained and it takes very little increase in dissolved CO2 to lower the pH of the fish containing water inside the bag. It is not high enough to kill the fish but it does two things; 1, pH is lowered which renders ammonia less toxic and 2. CO2 is a natural fish anesthetic in the low doses that accumulate. This is a happy coincidence. The same thing happens on regular bags. If it did not then fish shipping would not be practical as it is done today in an enclosed bag. Before modern shipping methods were developed fish were shipped in none air tight contaainers where oxygen levels were maintained just as they are in aquariums but the transit times were much longer as were the fish losses higher.
There has been quite a bit of study done on this subject. This has also spawned another controversy. Whether it is better to immediately add the fish to better conditions or prolong their stay in the shipping bags. Unless there is a very large difference in temperatures I adhere to the dump and dash method of releasing my fish from shipping bags.
Larry

 

[Kathy55g]

Not meaning to contradict, but this from Novalek:

The Kordon ® Breathing Bag represents a new approach to the problems of shipping live fishes and other aquatic animals over long distances or for extended time periods. The product development staff at Kordon, teamed with plastics chemical engineers, have taken a technology first developed in space/military research and refined it to produce the bags being offered today. The Breathing Bag allows the transfer of simple and complex gas molecules through the plastic wall of the bag -- carbon dioxide and oxygen in particular, as well as other gases - providing a true "breathing" bag in place of a "barrier" bag. As long as there is a normal breathable atmosphere outside the Breathing Bag, the animals inside will not run out of oxygen. 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. Kordon has shipped millions of bags (termed "Sachets") of living foods (tubifex worms, brine shrimp, daphnia, glass worms, etc.) for aquarium fishes using the Breathing Bag technology.

 

[Luis A M]

Interesting subject for home research

 

[apistomaster]

Hi Kathy,
Now that you mention it I do remember reading that when I was ordering from Novalek. I stand corrected. That makes the case for their use wherever appropriate even stronger.
From personal experience I know that fish shipped in them can live for an incredibly long time. Regular bags are the ones that experience the CO2 build up. But I am always open to constructive criticism of my pontifications. You got me on this one.
Larrry

 

[Kathy55g]

Hi apisto,
I am not meaning to criticize you. Sometimes the advertisement of things does not measure up to reality of them. I just wondered if you had some experience that contradicted that literature.

I didn't mean to "get" you. I appreciate the information you brought here.

Do you think that clownfish (A. Ocellaris) are too spiney to ship in them?

Kathy

 

[apistomaster]

Hi Kathy,
You did not say anything that wasn't well founded.
I find the bags to be quite tough and I think clowns would be safe to ship in the breathable bags. I would recommend a home trial and bag one up and leave it in the bag for 48 hours just to build experience and confidence in these bags. I would bag them individually always.
Larry