Reef Chemistry Question of the Day #12

Randy Holmes-Farley

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Reef Chemistry Question of the Day #12

While ammonia is not generally a problem in established reef aquaria, it can be a problem in both shipping of organisms, and in the early stages of an aquarium.

What is it about shipping fish that could make 1 ppm total ammonia less toxic than it would be to those same fish in 1 ppm total ammonia in the aquarium itself? Assume that the fish are exposed to the ammonia for the same period of time.

Happy Reefing. :)
 
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tyler1503

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I'm sure this isn't right, but here's a theory anyway!
In the aquarium there are (usually) other fish. Ammonia is likely to cause some sort of stress. 2 stressed fish are more likely to fight each other than a single fish in a bag....after all who's he gona fight with?
That, along with being in the light of the tank doesn't help. When they're being shipped it's usually in a dark environment helping the fish stress less. Less stress = lower chance of disease kicking in.
 

cope413

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My guess is that there's a difference in free ammonia since you said total ammonia. In the bag, O2 will drop, which means ph will drop. Lower ph means nh3 will convert to nh4, which I believe is less toxic (or not toxic?) To fish.
 

nphsmith

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I have a vague memory that the danger moment is when you open the shipping bag, thus enabling gaseous exchange. pH will then go ?up? Which will cause more of the Ammonia to be free and therefore more toxic. If I'm right, then fish in bags during trip will have less free ammonia due to lower ph.
Which may all be nonsense.
 

leptang

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There might might be less H+ from lower pH in a closed shipping bag deprived of oxygen there for NH4+ might be the form of less toxicity. NH3 + H+ ←→ NH4+ changes fast in a open air system with H+ being abundant NH3 the more toxic form will be more in a start up tank.
 

saltyphish

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My understanding is when the bag is closed air tight with oxygen trapped inside there is no extra room for gas exchange. This prevents the ammonia from becoming toxic to the fish. As soon as the bag is opened the clock starts ticking.
 

beaslbob

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Reef Chemistry Question of the Day #12

While ammonia is not generally a problem in established reef aquaria, it can be a problem in both shipping of organisms, and in the early stages of an aquarium.

What is it about shipping fish that could make 1 ppm total ammonia less toxic than it would be to those same fish in 1 ppm total ammonia in the aquarium itself? Assume that the fish are exposed to the ammonia for the same period of time.

Happy Reefing. :)

different kind of ammonia in a different environment (lower ph?)
 

mattvisocky2003

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Ionized vs un-ionized ammonia. The amount of harmful un-ionized ammonia available decreases as pH decreases and pH decreases as oxygen decreases. Which could lead to its own problems.
 

cheezybuda

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The lack of air exchange will cause a build up of CO2, which will be in the dissolved form carbonic acid. The build up of carbonic acid depresses pH. The drop in pH drives the ammonium ion to a free ammonia form.
 

leptang

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There might might be less H+ from lower pH in a closed shipping bag deprived of oxygen there for NH4+ might be the form of less toxicity. NH3 + H+ ←→ NH4+ changes fast in a open air system with H+ being abundant NH3 the more toxic form will be more in a start up tank.
i think i maybe wrong on the above. with H+ being lower with a high ph so i might have it all backwards lol. Still not sure how NH3 + H+ ←→ NH4+ converts
 
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Randy Holmes-Farley

Randy Holmes-Farley

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Very nice responses, and it's good to see folks trying to work through the chemistry.

A fish in a bag releases carbon dioxide into the water. That additional carbon dioxide (not the reduced O2) lowers the pH.

The lowered pH converts more of the more toxic free ammonia into the less toxic ammonium ion. It is less toxic because, being charged, it does not cross the fish gills as well.

So the fish in the bag are exposed to less free ammonia than are fish in an aquarium at the same pH.

It is true that aerating the fish bag when acclimating will bring up the pH and expose the fish to more toxicity.

One way around that is to prepare water of the same temp and salinity as the bag, and immediately move the fish to the clean water, then acclimate that clean water plus fish to the tank water conditions.

Happy reefing. :)
 

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