Magnesium and calcium levels

[Metrontech]

So then do I need weekly water changes?

Is there a pro and con to not doing them?

I mean if my levels are food why bother?

[Aquattro]

Yes. Water changes replenish elements you don't test for and dilute the build up of nutrients. Reefing isn't just about Ca and Mg. 20% biweekly will likely cover all your needs, and you save a whack of cash not having to dose. Consider yourself fortunate!