[daniella3d]

I do them once a month. I dose for alkalinity and calcium but when I do my water change I usualy have to cut down the dosing for a few days.

20% once a month work well for me. I can see when the corals need a water change because the vigor is a bit off. If you see no ill effect then you probably don't need to do a water change that often. It all depends on your own aquarium need and chymistry.