There are different schools of thought on this one. Personally, I keep my Q-tank cycled with the addition of ammonia when there are no inhabitants. If I do have a problem w/ disease from a fish that i quarantine and a i need to break the tank down, I have enough colonized media on-hand that I can just add it to the tank after setting it up again to avoid toxin spikes.
I recommend setting up the Q-tank like any other tank w/ decorations and hiding spots as well as a substrate to make the fish feel at home in the 4-6 weeks that it will be spending there. I don't need to exacerbate the move by having a stressful Q-tank.
Definately have the tank setup and ready to go before you get the fish.
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