I am starting a sw tank with live rock and sand. I added water and salt to the tank, my SG and tenperature reading were on target. When I added my live rock and sand, my SG reading was high (off chart). I am getting good foam from my skimmer. Is this normal? I took out some of the water in the tank and replaced it with some treated fresh water. It seems to be okay now. I may buy a refractometer, I donn't like the variation in my hydrometer.