I wish I could set up my 10 gal. which is currently residing in storage in the basement but I don't really want to go out and buy new heater/filter for it yet...I do plan on setting it up before I get new fish for my 55 as I don't want to lose any expensive cichlids...I have never qt'd a single fish in that's in my 30 gal. but I've never seen any diseases...I must really trust my lfs...if you can find a cheap 10-20 gal. tank with filter and heater set it up as a qt...better safe than sorry...I seem to be living on the edge...
I also don't. I just look very thoroughly at the fish in the tank and pick the healthiest fish only. Go for it though if you can find a tank kit. Usually petco carries 10 gallon kits for $60.
I didn't before because it was a new tank and it seemed silly to start QTing fish when I'd be purchasing 1-2 every week. Now that I'm nearly stocked however I've held off on buying new fish until a QT tank can get set up.
I must confess I normally do not qt new fish. I figure they have gone through enough stress from being shipped and then being stuck in an overstocked LFS tank so I like to bring them to a good home immediatley rather than put them through yet another temporary arrangement. I keep a close eye on new fish though and remove them if anything looks awry.
I also like to let the LFS function as a quarantine of sorts as I normally will wait several days after I first see the fish and come back and buy it if it still looks healthy.
I do have a 10 gallon quarantine tank that I use for QT'ing some of the fish I receive. I shop at a select few stores mostly where I trust the quality of the livestock I receive and the processes they use for QT'ing the fish before they go on sale. However that being said I do sometimes shop at other locations and those fish are always quarantined with no exceptions.
When quarantining fish I usually acclimate them to the water over a period of 30-45 minutes. The waters salinity and temperature is incresed over a couple of days to 84F and about 1-2 tsp of aquarium salt per gallon of water. If there is any noticeable indicator of disease I usually start treating with Para-Guard (R) for 7 days at the recomended dosage. I use this methodology to treat my fish as there are sometimes scaleless fish in the mix and most of the other meds on the market are fatal to them. This mix so far has done me quite well. QT time will vary from a minimum of 7 days to 14 or so.