Directions are below, it does seem to take a lot to raise MG compared to others like calcium, alk, etc. I would personally use the BRS 2 part, its probably of better quality, and they have a very precise calculator to determine routine dosing, but to each their own. Regardless of what you use, you need to test your MG (or whatever you're dosing). Test it first, dose as the instructions indicate. Test again a few hours later; this way you can judge the impact of how much you dosed. Keep adding the recommended amount each day and retesting until you get within the window you want. Its very important to not add all of the required dose at the same time. An abrupt swing won't bode well for your system, regardless of what you're dosing, gradually increase or decrease your levels to the proper levels for best results.
Directions:
Important: Shake vigorously immediately prior to use! The preferred method is to test the magnesium level in your aquarium, then add Tech M at the rate of 1 ml per gallon aquarium capacity per day to bring the level to between 1250 and 1350 ppm. This will raise the level by 18.4 ppm per day. As a routine supplement, if not testing, add two teaspoons (2 capfuls or 10 ml) per 50 gallons tank capacity every week in all marine systems.
