I would suggest that if you don't want to mess around with dosing yet that you switch to a more reef-suitable salt. H2Ocean is affordable, yet very good right out of the bucket. It's a tad low in magnesium, but it's passable. If you want to stick with the Instant Ocean you can buy a tub of calcium and magnesium and add those to the freshly mixed saltwater before adding it to your tank. I used to do this, and if I recall correctly, I used to add 80 mL dry calcium carbonate and 180 mL dry magnesium chloride to 15 gallons of freshly mixed saltwater to get the numbers to come out correct.
EDIT: I didn't read the second page before posting. Good to hear the H2Ocean is working out for you!
