Ahahha lready have him acclimating while i set up the qt. Think i could keep him/her in a 10 gal for a few day or do i need to get the 20 gal out of the shed ?
I would probably get the 20g, 10g seems too small. I would definitely try and hurry the process up though as it'll be very stressed in a tank that small. I would also keep something heavy on the lids (or duck-tape them like I do) since it will try and jump quite a bit.
That's what I do with my larger fish. I check for external parasites and if there aren't any I throw them into the big tank. After about a week if they don't start eating I watch them closer for internal parasites. Haven't had a parasite problem in my main tank yet, so that method has worked pretty well for me.