BEGINNER: Use 5 g (1 level teaspoon) per 80 L (20 gallons*) twice a week. Dissolve in at least 250 mL (1 cup*) of freshwater. ADVANCED: Check magnesium level, then follow addition regimen above until magnesium is adjusted to 1200–1350 mg/L. Each 5 g/80 L will raise magnesium by about 5 mg/L. Amount or frequency can be adjusted, but do not exceed 25 g/80 L per day. Thereafter, use as required to maintain magnesium. EXPERT: After determining the magnesium depletion rate, set up a continuous drip system. Use the following formula to determine how much to add to your top-off water: g=vm/80 (g=grams to add to top off water, v=volume of tank in liters, m=amount to raise magnesium in mg/L). For example, if you want to raise magnesium by 10 mg/L in a 200 liter tank, then you would add (200x10)/80=25 g into the top-off water. [For reference: 1 gallon*=3.8 liters, 5 g=1 teaspoon]