Thanks for this great guide. I would follow the months long process if I were adding to a large and established display. In the past, I did no quarantine at all, because I was not yet well educated on the benefits.
I'm starting up a 10 gallon nano and will be doing only 1 - 3 small fish, and adding to a new tank, so following the shorter BRS style 80/20 is going to make more sense for me I think, rather than a very long quarantine. The only issue is that furan-2 is no longer a thing. Is Seachem polyguard an acceptable substitute, or is it better to use pure nitrofurazone?
Quarantine processes are always a balance of efficacy and effort. The BRS process is faster/easier, but not as comprehensive. No quarantine at all is of course the easiest thing to do, that's why so many people skip it. I have a different quarantine process in place at work that takes up to six months - because the system I am moving new fish into has tens of thousands of dollars of fish in it and I must lower the risk even more than the process we use here.
That said, unless the fish are showing signs of acute bacterial infection, you should not use antibiotics as part of any quarantine process. Close to 100% of external bacterial infections in fish are caused by bacteria that is normally present in aquariums. There is also the risk of developing resistance to antibiotics.
Jay