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Discussion Starter · #1 ·
Sorting through some old notes today, I found a clip from a thread that raises a question I've wondered about, but never got around to asking.

In it is described an experience from someone who ran a LFS. He received shipment of fish, which he was too busy to properly deal with right away, so he opened the bag and put in an aerator. This resulted in the rapid death of all the fish!

He goes on to describe what he thinks happened. The water in the bag was laden with both ammonia and CO2, accumulated during the shipment. The CO2 was dropping the pH enough that the ammonia was held in the weakly toxic ammonium form. By adding the aerator, he drove off CO2, which raised the pH, and converted the ammonium back to strongly toxic ammonia.

Sounds feasible.

If so, then this might also happen with a shipped fish if you do a drip acclimation, with CO2-unenriched tank water that is naturally high pH. Even if death doesn't result, it could cause some stress, which is better off avoided.

Obviously, adding a dechlorinator that's effective against chloramines, and therefore ammonia, is a good idea.

So how much should one use in relation to the recommended normal water change dose, in order to detoxify the highest amount of ammonia that might conceivably be present? In a small water volume, is it possible to dose too much, so that the dechlor itself might have a toxic effect?
 

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with most water conditioners, moderate overdose is nto an issue. If you are super concerned, stop by your local pharmacy and see if they will give you a dropper or a 1ml syringe so you can dose a partial dose.
 

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with most water conditioners, moderate overdose is nto an issue. If you are super concerned, stop by your local pharmacy and see if they will give you a dropper or a 1ml syringe so you can dose a partial dose.
I use syringes for prime, excel, plant food and flux for my reflow soldering, so they come in handy for everything I do on a daily basis. lol.


It could be a valid theory. Ammonia is converted to ammonium in a low pH water. As the pH goes up, the ammonium looses a hydrogen atom and become ammonia again and become toxic, or something like that. lol.

I know some shrimp shippers ship with a little ball of purigen to absorb anything that comes up in the water during transport but for the mass shipper, that's an extra cost they don't want to bother with.
 

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That's right. Ammonia has a logarithmic dissociation constant of 9.23 (aka pKa value) which means at a pH of 9.23, half of the total value is ammonium and half is ammonia (at standard temperature and pressure). Since it is logarithmic, the percentage quickly changes over a pH range. For example, at a pH of 5, the ammonia is only 0.0074%, while it's 0.59% at a neutral pH, and 37% at a pH of 9.

I think most dechlorinators recommend not exceeding 4-5x the standard dosage. I'm not sure what the harmful effects of dosing more than that would be though.
 

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Discussion Starter · #5 ·
Ok, sounds like dechlor at three times normal dose might be a good compromise between potential overdose, and being able to knock out plenty of ammonia.

GeToChKn, I haven't heard the Purigen trick before. Will use that if I ever ship a fish.

If you are super concerned, stop by your local pharmacy and see if they will give you a dropper or a 1ml syringe so you can dose a partial dose.
Already have them. I find them indispensible for dispensing. :)

In case anyone who reads hasn't heard this trick, it's easy to dose accurate sub-mL amounts too. One mL of chemical plus nine mL of water, mix well. Then dose 1mL for each 0.1mL of chemical you need.
 
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