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Calmag with RO water and Hesi soft-water nutrients?


New Member
Hi Guys,

Our well water is unusable so we've just dropped in a a high-end RO filter. The water is coming out with a TDS of 20ppm and pH 7.

I have Hesi soft-water nutrients, so in theory they should have everything I need for use with RO water.

However, I've read many threads suggesting to add calmag to RO.

Just to be safe, shall I bring my RO water up with calmag to 150ppm and then add the nutrients?

My concern is adding too much calmag.



New Member
I have VERY soft water also, and have found that plain HesiCoco contains enough of cal and mag, that you don't have to add them unless the strain is calmag whore(as some are), if the plant asks for some more, I usually give it 1/4 or 1/2 dose of TnT CalMag. But rarely I have to add anything.. 3ml/ltr on veg and 5ml in flower, and the plants are happy..


New Member
Silly question, but can you give them too much calmag?

So ideally I shouldn't add anything unless I start to notice a deficiency in the plant?


New Member
That's what I do.. And I haven't had any toxicity either. Just go on the light side with calmag

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Well-Known Member
I use Calmag with every water change I also u ro water sitting at ph o 7 and a ppm of 14 now I don't know your lineup but I've bin using general hydroponic I don't like it but it works for now here is a chart I have used with grate results as u The need for cal-mag actually changes throw out the grow hope this helps

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