I don't do long drips or bag floats in tank - both situations are stressful to fish re the confined space, vibrations etc (there's published reports re increased cortisol levels (stress hormone) & rapidly increasing external parasite counts (taken from skin & gills) when fish are kept in these conditions ... in fish, stress significantly depresses the immune system)
If you prefer to acclimate over hours, water should have some
gentle current (air driven sponge (cycled from main tank) is best, airstone at least).
I transfer fish to a hang on tank container (no possibility of bag collapse or dumping into the tank)
- allow ~10 min for temp adjustment
- then add ~ 50% volume tank water (ie double the water level in container)
- at ~20 min I'll pour off half the water in the container, then refill with tank water (this should now be ~ 75% tank water)
- at ~30 min I pour fish & water into a net in small container such that fish are "swimming" within the net in this container, then transfer to tank with minimal air time
I hold/place net in tank so that fish can swim out when ready
If I don't already know shop water conditions, I'll check bag water with one of those 5in1 test strips (ammonia, nitrites, nitrates, pH, GH, KH) at the start - I'll often cut the test strip in half so as to use same strip for both tank & shop water.
If fish have travelled any distance, I'll add a 5-10X dose of Prime into the shop water BUT if travel (bag) water is "bad", the best course of action is just to net fish & place in clean water as quickly as possible, nevermind a slow acclimation process
Generally the main problem with shipping water is
ammonia, fish may arrive with burnt/melted fins, body lesions, significant gill damage - it's best to place these fish separately in a hospital tank & keep them in dimly lit, highly oxygenated water (cooler water holds more oxygen so always choose the lower end of fish comfort range); don't feed for 12 - 24 hours & then only small amounts (fish digestive system may also be compromised)
If the shop water shows high nitrates, just carry on with the usual acclimation process.
I don't add "sensitive" fish species to new tank setups, there is much more to an established tank than just the presence of nitrates rather than ammonia or nitrites.
Much more conservative to add a "tough" species to new tanks
neons guppies or endler guppies
depending on the source, all of these maybe more/less sensitive - look for
fish that are active & outgoing in the shop & have been in for at least 2 weeks (some shops run quarantine tanks/areas but none in my area do, I quarantine all new fish for at least 2 weeks before adding to an established tank)
Note, if your shop has no quarantine process or separate systems for incoming fish, avoid fish that have been in for 2 weeks IF new fish have been added to system tanks the day before - instead wait a few days for any diseases to manifest
(it's best to phrase your questions casually,
did any new fish arrive? rather than
I want fish that have been in the shop for 2 weeks )
When planning/adding new fish, I always perform a large water change the day before, then do ~25% daily water changes for a few days - if fish are slightly under the weather, lots of fresh, clean water is the best medicine (cheapest AND most effective
)
If shop is new to you, you might take in a sample of your tank water & ask them to compare this to shop conditions - note that some shops will keep various fish in different waters (especially guppies, mollies, platies may be in slightly to heavily salted water)
If possible, check shop water conditions some days before purchase, then you can plan acclimation (or even alter your tank to shop)
A quarantine or hospital tank really is a good investment if you like to add/change fish, or find a shop that quarantines fish, or keeps fish in individually filtered tanks, or runs UV and ultra-filtration on banked systems.
Healthy fish are very able to adapt to new situations.