You will hear a TON of folks chime in with "oh I didn't and it was fine!" feel like risking it? I never have...
Same with "I never QT my fish/corals/inverts and never had a problem!" feel like risking it? I think yer following me by now.
I wont tell ya the easy way, or the way that means less time or effort, I will tell you the way that I know works and wont go wrong.
Definitely check to make sure it doesn't leak, I made the mistake long ago with a new tank and got it filled all the way up with salt water, live sand and rock to find the seam on the bottom right corner was slowly leaking! Especially a tank that small its so easy, bring it out back and fill it up with the hose on cement so you can see if it's leaning or not. Just my .02