Lets talk RO/Distilled water

There are watering days and feeding days. Since RO or Distilled is pure water with nothing in it, no minerals, etc it is the best water to use to build the type of solution we want to use when feeding plants. But what about when we just want to water our plants? RO water tries to reclaim those minerals back by stripping calcium and magnesium from the roots of plants which is bad.

I have played with varying amounts of Bush Doctor Cal-Mag (2.5 & 1.25 ml/gal) for my water only days. The recommended amount is 5ml/gal applied at first signs of buds and apply not more than once per week, so I am obviously NOT following the directions. I do have an email to them about this issue as well. Directions do not address the type of water used and a search of the Fox Farm website has no articles addressing any use of RO water that I could find.

Although I have been playing around with this issue for a few years yesterday I found this How To Grow Cannabis With RO Water? - GrowDiaries
They suggest adding Cal & Mag until the PPM is between 100 - 150, which seems reasonable. Later when the plants start to bud I will provide that additional 5ml once per week.

I mixed 4ml/gal Cal-Mag worked out to 111ppm.

Anyone else see using RO water without adding Cal & Mag an issue, if so what do you do?

I grow autoflower plants only, indoors in a 3x3 grow tent. Plants are on a 20/4 light schedule and currently my new 2 Runtz girls 9 days old are getting 340 PPFD/30 DLI.

Happy New Year.

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It is. Among the minerals in tap water are calcium and magnesium; therefore cal/mag supplementation is necessary. It’s difficult to harm a plant with cal/mag, so I begin cal/mag supplementation when PPM reaches the point where I start feeding. I pay no attention to cal/mag PPM and simply feed 5ml in each feeding.

You might want to consider upping your lighting.

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I use RO and start full dose of cal-mag supplement, 5ml per gallon with every watering. I haven’t had any issues doing so, but can’t guarantee that someone else hasn’t had issues.

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What would you suggest?

These are seedlings and from my research that might be a bit hot. I will be raising the intensity probably to 900 ppfd at the highest.

I use store bought RO water… As I rent and have well water.

I feed water to 10-20% runoff with nutes at 6.5 pH twice a week.
Once a week in between feedings I water with Recharge pHed at 6.5.
I also add to the water Tribus Original.

For flushes…I add a little bit of my well tap water and pH to 6.5.

My calmag is only used on feeding days.

Here’s a feeding schedule I customized for mainly FF nutes.

I use Roots Organics Original soil… No nutes until about 4 weeks or so into veg.

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@Outlaw Thanks for posting that… I couldn’t find my copy.

Thank you

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Much appreciated