Quarantine tank set up

There is no need for active bio media, just each time you do a water change swap the water in your Quarantine tank or plastic tub for the water change water from your display tank.
Dose hydrogen peroxide of one drop per hour or when you can to elevate oxygen and use ammo lock and convert ammonia to harmless ammonium when treating the fish with copper chloride.
If only ever  fish, always have slight levels of copper chloride in that water ready to treat.
If with inverts, leave out the ammo lock and copper chloride.