Water chemistry in your saltwater reef aquarium is extremely important. Targeting specific numbers is not as critical as keeping your tank parameters stable. If you want to adjust your aquarium’s water parameter make sure that you do it slowly. Changing your parameters quickly is generally asking for trouble. See the chart below for my recommended water parameter ranges.
Temperature ~ 77 to 83 degrees
Specific Gravity ~ 1.023 to 1.026
Alkalinity ~ 7.0 to 10.0 dkh (2.5 to 3.6 meq/l)
PH ~ 8.0 to 8.4
Calcium ~ 350.0 to 450.mg/L
Magnesium ~ 1200 to 1380 mg/L
Ammonia ~ 0.0 mg/L
Nitrite ~ 0.0 mg/L
Nitrate ~ 10.0 mg/l or less
Remember when adjusting your alkalinity, or calcium levels that they are connected. Generally if you raise your alkalinity, your calcium will go down. If your raise your calcium, your alkalinity will go down. Furthermore your ph can go or up down with your alkalinity level so be very careful when you start dosing a 2 part solution if you are try to maintain or adjust your calcium and alkalinity numbers. Magnesium also plays a role in all of this. Be careful and make any changes slowly and see how your aquarium responds to any changes you make.