Eating?! Sleeping?! Using the restroom?! It's got to be one of those. I hope "shower" falls in there, too. All of this should occur, of course, after you set up that 600g tank!!!!
Seriously though, how are you going to do it? Just get the dry goods set up first? Will you do 600g of freshwater and then cycle it? Or will you dump everything over and then top off with fresh saltwater? Are you worried about kicking up any hydrogen sulfide from your sand?