So i got this guy here

hes yellow but its a crappy pic.
Anywho, i got him in that little shack for now cause i couldnt resist gettin him but my 15g isnt set up yet and the other one i wanted at petsmart looked not so hot the second time i looked at him. So how long should i let my tank im settin up now run for before puttin him in? And would just sparaying out the tank i just bought be good enough cleaning before i start adding gravel and all that?