Mark, keep it in QT
and keep doing water changes.. Tap water is fine, but you need to get a larger container so you can make enough for a couple changes and still aerate for a good 12 hrs.
Seriously, I know it seems like you should just add it to the main to increase it's chances of survival but you would definitely risk losing all 3. Imagine trying to keep the nitrites down if they were all in QT
Keep doing frequent large changes and you'll come out on top.