Raising Alkalinity requires you to dose Sodium Carbonate. The best value is to use Baking Soda, the same stuff you use to bake cookies, or remove bad odors from the fridge. Arm & Hammer Baking Soda is inexpensive, available at the supermarket and simple to prepare. Right of the box, it is Sodium Bicarbonate, but if you used it 'raw' it would lower pH while it raised alkalinity. What you want is Sodium Carbonate, aka Soda Ash, because it raises alkalinity and pH simultaneously. To make your own Soda Ash, all you do is spread out a box of baking soda across a cookie sheet, place it in an oven at 300°F for an hour, and that will drive off the trapped CO2 in the product. Allow it to cool, and place it in a sealed container until you need to use it.
If you want to make a gallon of solution, 2 to 2.25 cups per gallon of RODI water would be the proper strength for a dosing system, be it manually or with a dosing pump.
If you wanted to raise alkalinity in a batch of fresh saltwater, roughly 1 tablespoon per 10g of water should raise the saltwater's dKH by 1 point. Your mileage may vary. Always mix up the soda ash in a glass of water, stirring it well until it looks clear. Then pour it into an area of high flow so it mixes into the full volume of saltwater, and retest in a few minutes to see if you've reached the desired level. It's always best to under-dose and add more until you learn how much you'll need exactly.
Note: Do not buy Baking POWDER, you want Baking Soda.
Read more here: http://reefkeeping.com/issues/2006-02/rhf/index.php