The main reason why one should never use the drip method, is due to the fact that the water in the bag IS funky. Drop & plop is the safest manner in which to acclimatize fish, no matter where they come from, or how long they have been in the bag. A small swing in temp will have little to no affect on fish either, especially if one is going from cooler to warmer, which is typically the case. pH shock is non existent, so unless the TDS is way off there's no real concern there either. I have seen fish imported from all points on the globe, Africa, SE Asia, Europe, etc, with some of these fish valued in the thousands of $$$ (for a single specimen) and every last one of them went straight from the bag, straight to a holding tank, and I have never seen a single mortality from doing so.
The term "pH shock" is a total misnomer.
What one really needs to pay attention to is TDS (total dissolved solids). Moving fish from water with low TDS to high TDS is usually tolerated fairly well, where as moving a fish from high TDS to low TDS can often cause a great deal of osmotic stress, even death.
If one looks at this from even a common sense approach, if what some people stated about pH shock was true, most fish being imported in from outside of the country would be dead long before you opened the bag, as the vast majority of exporters do not use long term pH stabilizing agents when they bag the fish, and after 24-48 hrs the pH in those bags has definitely dropped, in many cases by a significant amount.
In shipping situations this is a good thing, as the lower pH protects the fish from ammonia. Once the bag is opened, and C02 escapes, the (fish safe) ammonium, converts to ammonia, which can be toxic to fish at higher pH values. Hence the reason that most importers pay more attention to the water temp of the bag than anything else, and in the vast majority of cases simply open the bags, net the fish out, and drop them into their holding tanks. Experienced commercial importers learned a long time ago that the quicker you get the fish out of that toxic soup in a bag, the better.
