In my tank, I dose 2.5mls a week to maintain stronium at 7ppm. The clams absorb so much cal. And the difference between the molecular structure between cal and sr. Is not much different. This is why they don't know if it is a toxin absorb by mistake. I have noticed the corals are stronger since dosing sr. A lot of talk is still unknown if low levels are bad, no one has done tests on it, I'm not going to be the guinea pig with my tank and clams. Every place I've researched says clams need sr. But if your coral tank is light I suppose you wouldn't have to dose. W/c would work for everything at that point.