Now you're cooking! If you can use your tap water and the ph stays stable then you don't need CalMAg at all......CalMag replaces calcium, magnesium, iron etc that is taken out of your water when it is distilled or put through an RO system. Plants NEED these minerals and ingredients for good health.....and they are usually in abundance in tap water.

When using tap water....check ppms BEFORE you add nutes, add your correct number of nutes in ADDITION to that number, then check and adjust ph last....always ph last.

The largest issue people have with certain types of tap water (and why it is often not used in hydro) is that certain types of water will not stay at a stable ph.....so when you remove EVERYTHING from the water you can control ph any way you want. But the catch is that certain things the plant NEEDS will have to be put BACK in with supplements like CalMag.

IF your tap water will stay stable (at close to whatever ph you put it at to start with) then you are good to go and don't need CalMag at all......just your nutes.