For initial set up, you can mix the water in the tank. You can't do that for PWCs though. Put in water to a little over half full, salt, heater, powerheads and set up filter. After water is correct salinity and temp, put in the rock if you're gonna have some. Then the sand. you might have to top off the water, depending on how much is displaced by rock and sand. Start up the filter (or sump). Then toss in some raw fish or shrimp- or pour in your liquid ammonia, whatever you're using. Good luck!!