A well written post reflects how I advocate introducing new fish:
I use tank transfer for all new specimens to insure against cryptocaryon irritans.
The initial receiving tank is temp and sg adjusted to the bag water( sg a few points couple of points lower than the bagwater is ok but not higher) This obviates the need for drip acclimation and prolonged stays in bag water where ph can rise and ammonia toxicity can increase once the bag is opened.It is particularly important after prolonged stays in the bag.
During the 12 day tank transfer process ( 3 day stays 4 transfers) I observe for other maladies. Since there are no meds to interact with in the transfer tanks which contain freshly mixed salt water aged and aerated overnight , I can use an ammonia detoxifier during the 3 day period. Bound copper products for example can't be safely used with ammonia detoxifiers as more toxic free copper occurs with lethal copper toxicity,even though total copper measures the same.
If there is reason to suspect infestation with brooklynellosis, vlevet or flukes , I'll do a formalin bath before starting treatment with copper for velvet, foralin for brokklynella or prazi pro for flukes.
Since not all maladies will present symptoms in the 12 days( flukes can easily be missed ) ,I use a larger cycled qt tank for an additional 2 to 4 weeks of observation depending on the condition of the fish with treatment as necessary.
Most fish receive no medications yet all are effectively prophylactically treated for ich,the most common killer
Ammonia is monitored and has never been an issue during the 3 day stay but a detoxifier is added just in case, The cycled tank takes care of itself.
BTW there is no need to worry about nitrite or nitrate.