cool, really can't say anymore than the other guys said above.
- Start daily tests of alkalinity.
- If it is falling daily, then look at a calculator online for the product and dose to maintain a steady level
- Continue to test daily until all levels stabilize with dosing
- Test before and after water changes to make sure you don't have any drastic bumps in levels that will through you out of wack
Also, make sure you are dosing according to the ratios of the product -most products dose 1 to 1 the calcium and alk parts. This way you only have to test cal weekly after a bit because you know that if your alk is in line, then your calcium should follow as long as your mag is in a good range.
If your doing regular water changes, then you shouldn't need to dose mag. I rarely add any at this point.