Beginner : my bottol says " 1 level teaspoon per 40gal 2x per week. disolve in 1 cup of fresh water. check calcium level every 2 weeks and adjust amount or frequency accordingly.
Advanced : check calcium level, then follow addition regimen above until calcium level is adjusted to 380 - 420 mg/L. each 5g/150L will raise calcium tby about 12mg/L. quantity or frequency can be adjusted but do not exceed 10 g/150L per day. thereafter use as required to maintain calcium.
Expert : after determining the calcium consuption rate, set up a continuous drip system. use the following formula to determine how much to add to your top off water: m=vc/400 (m=grams to add to top off water, v=volume of tank in liters, c=amount to raise calcium in mg/l). for example, if you want to raise calcium by 25 mg/L in a 200 liter tank, then you would add 200x25/400=12.5 g into the top off water. [for reference: 1 gallon =3.8 liters, 5 g=1 tsp].
Notes : if used with reef calcium, it is not necessary to exceed 380 mg/L total calcium. use reef status : calcium to measure calcium.
HTH 
