+1 on depends on the source of the stock, where they're going among my tanks and what's in the tank they'll be added to.
Of course, after doing a 2-3 week quarantine on the last five chain store purchases building up the numbers of several schools of common fish and having zero problems crop up, I skipped QT on the last two neon tetra and just tossed 'em in my 20g set up. Yep. A week later: ICH. Major major ich.
Now I've got 20g worth of fish bickering and b*tching in a 5g treatment tank for the next 2-3 weeks, a pathetically empty show tank, and the joy of carefully monitoring the 20g once the fish are put back for cycle problems or recurrence.