It depends on what type of heater it is 
And I second the do nothing except for cycling the tank, adding liverock, getting your sump set up and the skimmer dialed in, etc.
As far as the specific gravity, the directions are always a little off. Mix it up and test it before adding it.
Just take some water out and replace it with fresh to get it where you want it. BTW, what are you using to test your SG? Refractometers are more accurate than the swing type floaters.
Jim
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90 Gallon glass, 135#'s of rock and 2" sand. 2-250w 20k XM metal halides. 2-95 watt actinic VHO, 4 powerheads, Coralife skimmer. Maroon Gold Striped Clown, Blue Chromis, Kole Tang, Pygmy Angel, Serpent Star, Brittle Star,Gorgonians, Mushrooms, Yellow Polyps, Turbo Snails & Blue Legged Hermits. 20 gal sump with Caulerpa, Mag 7 return pump. | 
