Salinity and SG will range, depending on what you have in your tank. NSW has a salinity of 35ppt which represents a SG of 1.027. For most reef tanks, a salinity of 34-35ppt (SG 1.025-1.026) will sufice. FOWLR tanks can get by with lower salinity levels, 30-33ppt (SG 1.021-1.024) Keep in mind that this is also dpendant on temp, but in the home aquarium itwill not matter too much. If you are using one of those "swing arm" hydrometers I suggest you bring it to the LFS and have them test it to their water using a refractometer. The swing arm models are notorious for not being accurate.