My quarantine tank is twenty gallon with Heater and borrowed sponge filter from established tank(s).No food or light for first 24 to 48 hours, no substrate,fake plant's (fish don't care).
Fish remain in quarantine for two to three weeks.
Medicate only for symptoms presented.
Have tried live plant's but some meds,salt treatment's, kill plant's which then foul the water.
Even a rubbermaid tub can be used for quarantine in a pinch.