Quarantine
A good quarantine consist of observation and proactive treatment lasting at least two weeks, prefer a month or even longer.
1)Observe prospective new fish at the LFS very closely, physical appearance/condition, level of activity, interaction with tankmates, respiration, feeding and etc...
Any dead/unhealthy fish in the tank or adjacent tank(s), don't buy any.
2)Before introducing to QT, give'em a strong salt dip/bath, this will force many external parasites to drop off the host.
3)QT should be kept at 87'-88'F and salted at at least 1tblspn per 5gal, this will eradicate any ICH and some parasites.
4)Feed at least one week with antibacterial food and then at least one week with anti-parasite/protozoan food.
5)During this time observe closely for anything indicative of illness/infestation, treat accordingly with meds or just cull.
6) I'd only do a complete tear down/sterilization for diseases like TB, Columnaris/Flexibacter and other such highly contagious/tenacious nasties.
For the most part if a problem is treated successfully, it is eradicated completely, no sterilization necessary.
A proper QT is alot of work.