Ranges I recommend for salinity, etc:
35 ppt salinity or 1.026-1.027 specific gravity (35 ppt and 1.0264 is average)
Temperatures from 79-82 degrees (82 is natural average)
I keep my tank at SG 1.025+/- @ 79F (average). I may bump it up eventually when I go reef. As previously stated, the average SG/salinity of natural seawater is 1.0264/35ppt.