Additions for RO water, especially Calcium

Nutrients
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I’m switching from tap water to RO water and trying to understand how that affects my nutrient solution. I currently use the method described in Bugbee’s maximizing cannabis yield video, which in summary is:

substrate: 50% peat, 25% perlite, 25% vermiculite, 1.4g/l dolomite lime, 0.35g/l gypsum, 1.0g/l wollastonite
nutrients: 120ppm Jack's Professional Peat Lite, 20ppm potassium silicate.

I use 15 gallon grow bags and autoflower seeds, so the roots have some room to spread out and access micronutrients in the substrate, and the autoflower seeds mean those micronutrients don’t have to last as long.

Peat Lite doesn’t have some micronutrients, particularly calcium. This system relies on calcium in the substrate (dolomite lime, gypsum and wollastonite all have it), and the tap water. My tap water doesn’t have much calcium or magnesium, but has a lot of sodium which interferes with adding other nutrients. The EC of my tap water is 0.92 which is quite a bit higher than I’ve been advised to use. I’m switching to RO water to change that.

It could be the substrate has enough of everything other than NPK that all I need in my nutrient solution is those, but I’m not sure. The sources I can find for calcium confuse me. At a primitive level I see calcium chloride, calcium carbonite, calcium nitrite and calcium sulfate. There are probably more. Cal-Mag products are generally made from one of these, mostly commonly calcium chloride. All these have issues. Some are not very water soluble, and the ones that are contain things that will throw off my nutrient formula (like nitrogen).

Jack’s professional also sells calcium chloride, but I saw a caution somewhere about the chloride part. It’s necessary for solubility, but the chloride stays in the solution and can give too much chlorine to the plant. Down To Earth sells liquid calcium 5% and only lists that in the guaranteed analysis. But a CSR says that product also has more than 8% chloride, they just don’t have to put it on the guaranteed analysis. I assume other cal-mag products sourced from calcium chloride would be the same. I’ve also seen cal-mag products from calcium nitrite, which adds quite a lot of nitrogen.

A couple more issues: I’m a medicinal grower and what I am doing now easily accommodates my needs, I’m simply trying to do better, but I’d rather not change too many things at once. Also, I am well-stocked with peat lite so I would prefer an answer that complements that rather than replacing it. I’d rather ‘fix’ my water than change anything else. That gives me more flexibility than relying on something designed for RO water.

I’m thinking to add a little bit of calcium chloride and epsom salts to my nutrient solution as I switch to RO water, but to do that pretty sparingly. Asking questions here is way faster than trying it with a grow, so thanks very much in advance for any advice you might have!

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Jacks has sufficient calcium.

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I’ve no experience with RO. But @Lostgirl has helped someone with RO water not long ago.

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To emphasize: I have used Jacks 321 with RO water for years without problems.

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Sorry, I think there is a bit of confusion here. JRPeters has several somewhat distinct product lines. The most common on this forum is Jack’s Nutrients, which is designed for cannabis. But they also make Jack’s Classic for general home gardeners, Jack’s Professional for farmers and a couple of specialized lines.

Professor Bugbee’s system uses Jack’s Professional 20-10-20 Peat Lite. I had a devil of a time getting this. There are no dealers for any of the Jack’s products on Hawaii Island. I wrote to the JRPeters CSR to see how I could get it and was basically told to switch to Jack’s Nutrients. She said Peat Lite did not have calcium. But it was what was in the Bugbee video, so I persisted. Eventually I got it from ebay. It’s sold in 25lb bags, so I have a many year supply. Jack’s Nutrients and Jack’s Classic I could get from Amazon if I wanted to change that much.

Jack’s 321 is part of Jack’s Nutrients, and does have sufficient calcium for RO water, even the version that isn’t labeled RO. I think the reason Professor Bugbee’s method doesn’t need calcium is that there is a lot in the substrate. Perhaps enough even for RO water, but I’m not sure about that. He could be getting some from the water too.

My tap water kind of sucks. I live on a volcanic island and our tap water flows through many layers of volcanic rock to aquifers deep underground. The volcanic rock is excellent at filtering out most things so our tap water is rated very highly for human consumption, but it won’t filter out sodium so the TDS straight from the tap is something like 600 ppm and does not have calcium or magnesium. Also, I live 50 miles downwind from an active volcano, so our rain water is acidic when the volcano is erupting. I want to start with RO water for predictability.

Jack’s Elementals sells soluble calcium and soluble magnesium, which might be worth adding to RO water. But the soluble calcium is sourced from calcium chloride. If you use that as a source of calcium you’ll actually get 50% more chlorine than calcium, which is probably too much. But that and calcium nitrite seem to be the forms easily soluble. I thought about using a premixed cal-mag product but they start out with calcium chloride so have the same problem, just with less transparency.

Since there are a lot of micronutrients in the substrate, I’m going to try using soluble calcium and soluble magnesium in the nutrient solution but at very low levels and see how it goes. Unless the experts here tell me I’m just wrong on something.

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I would not be adding calcium with ro water if you already have domolite lime and gypsum.

Adding calcium will almost always cause a problem down the line.

Only add in mabey early mid flower if the plant says she needs it. And its rare to experience the need. I’ve only ever had a chemdawg that was a calcium hog of the numerous strains I’ve grow out.

Best general practice is that adding calmag will damage your grow and is dangerous, so avoid trying to use randomly just in case.

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@stcapt Was curious where you learned of Dr. Bugbee’s system. Did you take some of his classes? I do know that he is constantly tweaking the formulas. I am taking the Medical Cannabis Cultivation and Technology class taught by Dr. Bugbee and Dr. Hines (with many other speakers) and know that he uses RO water in the lab, but tap water in the greenhouses. His tap water in Utah is very high in Calcium so he does not need it in his nutrients. He also mentions that he was using Black Gold peat…but was getting inconsistent ph values so switch to Premier peat. He is doing 75% peat, 13% vermiculite, and 12% rice hulls. He is talking about going to 25% vermiculite and using some minor additives to get silicon in the soil instead of rice hulls.

I just finished a section on the different types of lime. He is a fan of using fast acting hydrated lime to quickly get the ph where he needs it and then controls with the ph of his nutrients.

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I did not take the course, but wish I could :). I started with this: https://youtu.be/JwtkHxv_3pU?si=8witvCLztI_z4VIf

He has others and I tweak it a bit. At the time he was using 50% vermiculite and 50% vermiculite plus only dolomite lime and gypsum as addendums. The video also says I can substitute perlite or coir for peat or vermiculite, but I will lose some of the silica. I did substitute perlite for some of the vermiculite because I think it drains better.

There is a reddit group: r/BruceBugbee

That gives me some of the updates you mentioned, but not completely up to date. I can’t find rice hulls here, but I can find wollastonite, so I’m pretty close, although if the brand of peat moss matters maybe not close enough.

I do use black gold peat moss, but only because it’s what I found at my local Ace. I wasn’t worrying about the brand of substrate component, but I use Vigoro (Home Depot brand) for perlite and vermiculite and Down To Earth and Build A Soil for the addendums.

I did see a mention that he was getting calcium in tap water, which is why I was concerned. According to the county, our tap water is very soft. The volcanic rock filters out what makes water hard, which is calcium and magnesium. I tried to boost my calcium by adding a little micronized calcium carbonite to my nutrient solution. That was a fail, it precipitated out. TBH, I was having trouble with the PPM of my nutrient water already. I thought my meter was useless. But I measured the EC of tap with no nutrients and it was like 600. That alone should make it difficult to dissolve nutrients so I talked to a guy at the water department and a chemical engineer friend. Turns out the water department only has to report the things the EPA is concerned with and by that metric we have very pure water. But if you put salt in water, it separates and the chlorine evaporates away leaving you with sodium water. Since I live on a volcanic island some salt can creep in. EPA doesn’t care about sodium, but it does go into the TDS and plants may care about that when you add nutrients.

I still think the switch to RO water is good for me. It’s encouraging that Bugbee uses RO water in the lab. Did he say if he has to do anything to boost the calcium and magnesium there? That would really be a definitive answer to my initial post!

I think I’m going to start with @benripped comment and do nothing until I see a problem. If I have a problem I’ll gently add the calcium chloride and magnesium sulfate from Jack’s Elementals line and see if that is an improvement. It seems likely that my earlier attempt failed not because of the water, but because I used calcium carbonite, which isn’t soluble which means I’ve been on a wild goose chase. The RO water seems like a positive change anyway so I’m going to keep that and start adjusting from there.

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He does have to get it from something in his solution. He has gone into great detail about the forms and amounts of each essential element in his feed solution but we have not got to the part when he describes what products he uses and in what perportions to get to his ideal concentrations. That is still a few weeks out.

I just joined…thanks

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Don’t use vermiculite with plants because it can compact and suffocate the roots. Vermiculite is sometimes used for germinating seedlings but most people don’t touch it nowadays. Some sources of vermiculite have been found with asbestos so if you do use vermiculite, make sure it’s wet before handling it and wear a dust mask so you don’t inhale any dust.

Reverse osmosis water has no minerals in and you will need to add calcium and magnesium to the water to stop deficiencies. I use 1/2 a level teaspoon of Epsom salts and 1/2 a level teaspoon of calcium chloride for 8-9 liters (about 2 and a bit gallons) of water. Mix the Epsom salt and calcium chloride in a small container/ cup of hot tap water to dissolve them. Epsom salt doesn’t dissolve in cold water. Then add the water with calcium and magnesium to a watering can, add some more water and fertilizer and get the pH around 6.5. Then water the plants with it.

The chloride in minerals is actually a salt, not chlorine. Sodium chloride, calcium chloride, potassium chloride are all mineral salts that dissolve easily in water.

Calcium carbonate is what limestone, shells and dead coral skeleton are made of and it doesn’t dissolve easily in water.

Plants can take and use a small amount of chlorine but you don’t need to add that to the water.

The calcium chloride I use is for swimming pools and you can buy a bag pretty cheaply from a hardware store or place that sells stuff for swimming pools.

Most people use coconut coir now instead of peat moss. Coconut coir is cheaper and renewable whereas peat moss is increasing in price and becoming harder to get due to peat plants beoming endangered in the wild.

Peat moss tends to have an acidic pH (below 6.0) whereas coconut coir has a neutral pH (around 7.0).

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