Do You Really Need Cal-Mag in DWC?

Why

Your plants need calcium and magnesium. The question is whether they need an extra bottle to get them.

RO removes most of the minerals from your starting water. But you don't grow in that water alone. You add nutrients, and those nutrients may already supply both.

For example, I use the General Hydroponics Flora trio. FloraMicro supplies calcium, and FloraBloom supplies magnesium. So even with very pure RO water, those minerals are already going into my reservoir.

But here's the catch. Containing calcium and magnesium doesn't automatically mean supplying enough. The amount of base nutrients you use matters.

And your EC meter can't settle that question. It measures overall conductivity, not calcium and magnesium separately.

Check the complete feed, including all the parts of a multi-part nutrient system. Don't assume a mineral is missing just because it isn't in one bottle.

If your plants are growing well without extra Cal-Mag, using RO water alone isn't a reason to start adding it. If you already use it, healthy plants don't prove the supplement is unnecessary, either.

And a yellow leaf doesn't automatically mean you need more. Root conditions and pH can affect nutrient uptake even when the nutrients are present.

Adding extra just in case isn't automatically safer. Too much can increase salt levels and upset nutrient balance. A combined supplement also adds both minerals, even if only one is short.

Cal-Mag isn't an insurance policy. The bottle doesn't cover everything.

Researching this episode made me question my own routine. I've been adding Cal-Mag, but I haven't established whether I need the extra.

I'm going to leave it out and see how things go. That's an experiment in my own grow, not a recommendation for yours. I'll let you know what I find.

The takeaway? Your plants need calcium and magnesium. Whether they need a separate supplement depends on how much your water and base nutrients already supply.