I use salinity salt mix. It is some awesome stuff. You get way more bang for you buck than other salts. I use to use Reef Crystals and i have noticed much happier corals since switching to salinity.

salinity™ is a blend of salts specifically formulated for the reef aquarium that contains all essential major, minor, and trace components found in natural reef waters, but contains no toxic or non-essential components. Additionally, salinity™ is the most concentrated salt blend on the market. With a hydration level of <0.5% salinity™ will yield a greater volume of prepared saltwater at a salinity of 35‰ per unit of weight than any other salt mix currently on the market.

salinity™ is identical to the distribution of anions and cations found in Natural Sea Water (NSW). We have compiled data from all the oceans and seas on the Earth, and have targeted the midpoint of the range for each element. We guarantee to be within ± 3% of the midpoint. For example, at a salinity of 35‰, for calcium, magnesium, and strontium, we have the following targets and ranges.
Calcium: target 422 mg/L, range 409 to 435 mg/L
Magnesium: target 1336 mg/L, range 1296 to 1376 mg/L
Strontium: target 8.4 mg/L, range 8.1 to 8.7 mg/L

Alkalinity and pH values vary widely over the Earth’s oceans. salinity™ will be within the following ranges:
pH: 8.4 to 8.6
Alkalinity: 3.2 to 3.8 meq/L