QT Best Practices?

After my most recent ich outbreak that wiped my entire fish population clean, I've decided to take up the practice of using a QT.

Right now I have one tank raised clown in a 10 gall QT and he/she has been in there for about a week. I plan to leave him in there for about another 3 weeks to ensure it's parasite free. I haven't treated this new fish with any meds yet, so my question is should I treat him with external parasite meds even if he show no signs of disease? I'm not a big fan of uneccessary meds, but I don't know if I'm negating the purpose of a QT even if I wait for 4 weeks for signs of sickness. I've read conflicting opinions all over the net. The fish seems to be doing well dispite living in a QT that is cycling.

 

the best thing to fix the ick is neon goobies my tangs line up to get cleaned. i have a strwbry. bass. you would think he was dead floating when he is being cleaned.

 

I was thinking more along the line of is medicating fish as a preventative quarantine practice for new fish necessary if they show no signs of disease at the end of "x" amount of weeks. To treat or not to treat.