I added one dose already. But this is the first time I am adding the Reef Builder. My tank is already around 5 months old? Weekly water change about 10% only. So hard to guage. Anyway...Dunno why I am so particular about my kH and calcium....I'm keeping softies mostly. Ah..guess it's just to grow coralline algae. Those on my rocks are pink-red. Those on my glass are green! I want the pink ones!