When O2 hits the water in the bag when you open it, the pH shifts and causes the ammonium to turn into toxic ammonia. So you are still getting a rapid pH change and an ammonia spike with the drip method. That seems to be the argument against the drip method. I personally don't know which is correct at this point, just illustrating what the general argument is.
I don't know if squirting some detoxifier will help or not. Some do it and others say it's useless...like in the cichlid forum thread.
Why does it shift?
Due to CO2 or something else?
The only thing that would cause it to shift would be CO2 and the amount of cO2 in question here is VERY small relative to the air outside the bag I would suggest.
If the acids in the bag are high that would imply less NH3(more toxic) and more NH4+(less toxic).
Adding ammo lock is not a bad idea, nor would adding anything that dropped the pH some.
Adding that is no better either and those tend to have salts of some sort........
What is the large variable is how long have the fish been exposed to NH3/NH4 and at what concentration.
Time x concentration = dose.
If you are at the bitter end of a fish's death throes.......then perhaps, but unless you have a lot of NH3/NH4...........I am far from convinced of this argument.
I think the 1 hour of drip and dilution, as that pH goes up, you are adding new clean water and diluting the NH3/NH4 anyway.
That drives the pH down again.
But equilibrium pH depends on what?
The alkalinity................not CO2.
I think you have to have a very weakened fish to start with and hard shipping water, and poorly packed fish(too many per bag) for this to be a real issue as presented thus far.
CO2 can and does exchange out through those bags, so you end up with a much smaller pH change relative to ambient.
The more I think about this, the more it really seems like BS...............I want data and toxicology papers showing that drip is worst than dumping the fish in there with a range of pH's/alkalinity/CO2 addition or not and over the time frame in question, 1 hour or so.
You cannot say that much otherwise.
The small increase in NH3 for a brief period and then heavily dilution over that same time frame while the gases equilibrate using the drip method (which takes 1-2 hours with a drop checker FYI, let's say 30 minutes here) seems like they cancel eachother out fairly quick.
That issue was not addressed anywhere.
It I have 250mls of shipping water and have exposured the fish to 24 hours of shipping, say NH3 is at 0.1ppm, then airing it out, the amount jumps to 0.15ppm in 1 hour after opening the bag, we also have the drip tank water adding 500mls to this same volume.
Now assuming the tank water to have 0.0ppm, we now have 0.15ppm NH3/3= 0.05ppm and falling fast...........at the end of that 1 hour peroid, the pH will be that of the tank, and NH3 has gone from 250mls and 0.1 to .15ppm NH3/10x or whatever volume you do the drip method to, I add about 10x as much tank water vs the bag water..........0.015, or 15ppb. Pretty low and for a mere hour or less.
Leaving the fish in the bag another 15 minutes is worst..........I'd argue.
So it's like leaving the fish in the bag another 1 hour sealed or better ...............
Exposure is the key issue here and for how long and what other things are affecting the concentrations of NH3.
I do not see a long time of exposure, I do not see a large pH shift that is immediate(which seems to be assumed by these folks), I do not see the time dependency of the dilution factor included, rather, conveniently left out.......