qt tank per my way
scenario
main tank sick fish, i need to quarentine it, my main tank also supports the main tank filter and another filter unit that matches the qt filter unit (never leaves main tank) and media for the qt tank filter unit(media is well establised and maintained just like the main tank filter).
qt tank
small but usable to fish. set up like a normal tank but with little or without gravel hiding spot heater, temp stick, filter that matches the qt filter on the main tank, qt tank filled with dechlorinated water or good quality used tank water, filter on qt tank running for circulation and heater running. now before i put sick fish in i will take the qt filter media not filter unit that has been in the main tank in place in the the qt filter unit that is on the qt tank, whala now the qt tank has biological filtering. place new filter in qt filter unit on main tank so that it can start being colonized and can be transfered in case it needs to be used. now we can put ill fish in qt tank and medicate.
when ill fish is healthy, acclimat and return to main tank, throw away qt filter media that is on the qt tank, strip tank down and thuroughly clean it out, set it up again ready for the next time.