Hello John,

You can raise the pH of your reverse osmosis (RO) water by either using baking soda or a commercial buffer. As you said you would do this before adding your marine salt.

Ideally make up the water to match the main displays salinity, pH, alkalinity and calcium / magnesium for a reef tank.

You could use SeaChem Reef Builder to raise carbonate alkalinity without adjusting pH or to raise both carbonate alkalinity and pH use SeaChem Reef Buffer. Calcium and magnesium can then be adjusted with additives as required.

Hope this helps.

Mark
ATF