A small note, here...
I'm new at the whole reef thing, but I happen to work at a salt plant. Straight Water Conditioning salt, much like our Safety Salt (not saying where I work- but our salt starts with a W...) is just fine- it's pure salt, no additives.
Pelletized versions, however, have several additions, including a soap- type product that, I daresay, would not be conducive to Reefkeeping...