Need help with QT setup

[CDeatrick]

I am embarrassed to admit that we do not yet have a QT. Can you all give me advice on where to start with setting one up? Currently we have a 75 gallon tank with fish, live rock, a few crustaceans, mushrooms. We also have a 40 gallon tank with 3 GSP, 1 Porcupine Puffer, live rock (These will all be moved to a larger tank as we're aware the porcupine needs at least 100G). The fish, rock, etc from the 75G will be moved to the 350G once cycled. Do we use the 40G as a QT and if so, how do we keep it cycled?

 

[GoneReefin]

My main tank is a 90 but I’ve got a 10 gallon for QT with a heater and small wave pump only. Every 4-5 days I just do a 100% water change to keep the ammonia in check

 

[Sharkbait19]

As long as there is established bio media, the qt will remain cycled. I run my fluval 13.5 as a qt, before that it was an old 10 gallon. My dt is a 40 breeder.
40 gallon is a good sized qt for most fish, as when you get them they won’t be that large.
Fwiw a porcupine is going to need at least a 150-180 bare minimum imo. Very large and very active fish.