Please prepare a canister of 5 liters.
Dissolve 2 kg of Royal Calcium Chloride dihydrate powder in 4 liter of R/O water and then fill the rest with R/O water. Larger or smaller canisters can also be used, you will simply need to extrapolate the quantities added for each canister.
Depending on the volume of the tank each solution is now monitored manually in order to determine the actual levels needed. Before adding any solution, you have to determine the actual water values.
Example:
50 ml of this solution in a 500-liter tank.
Value before dosing = 400 mg of Calcium. After 2-3 hours repeat the test and have found that the Calcium value after the 2nd test is 420 mg of Calcium. In this example 50 ml of this solution increased the Calcium value by 20 mg/liter for a 500-liter tank.
Now program the dosing pump to add 7 ml of the solution once a day, so 50 ml of the solution will divide over a week.
In that way you can calculate the loss of Calcium as a result of coral growth and add the amount needed to achieve the required values.