Well there aren’t too many options for water soluble calcium. I think there’s mostly just cal nitrate, calcium chloride and calcium EDTA.
I’m already using calcium nitrate, which is great for getting the bulk of the calcium needed. The issue is that later in flower, plants continue to be hungry for calcium but their need for nitrogen starts to drop off and they want more potassium. However, potassium is also an antagonist toward calcium and magnesium. So you really need to keep the calcium at the ~2:1 ratio with potassium, while reducing the nitrogen.
If you add more calcium nitrate, you also increase the nitrogen so that doesn’t work. That’s where supplementing in calcium EDTA helps. It allows you to reduce the calcium nitrate you use, yet keeps the calcium level up.
I’ve also experimented with calcium gluconate, which could actually be even better than EDTA. It’s chelated with amino acids that the plants can also use; however it’s a lot more expensive, lower density and lower solubility. Calcium chloride you can use in very limited amounts. Adding chlorine isn’t something that’s generally desirable.
Edit: There’s also calcium citrate, which might be worth experimenting with. It’s probably cheaper than EDTA, but I do wonder if it would affect the pH. And also calcium carbonate – which I don’t think is any good for hydroponic applications.
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I got ya, whats the percentages of cal/nit in the edta you use?
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Calcium nitrate is 15.5-0-0-19-0
EDTA is 0-0-0-9.7-0
n-p-k-ca-mg
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Hmm, Mind linking me your vendor? I haven’t been able to find any other then those assumed due to too little information, that do not contain nitrogen. I currently use chelated calcium carbonate that has an npk of 1-0-0 with 5% cal because that was the lowest I could find.
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Yea, that’s why I was asking, since I’ve been using the calcium carbonate. I did research and found that it is derived from lime, so it has a tendency of raising the pH. Coco already has a pretty high pH so it was of a concern to me but I didn’t want to use calcium chloride for the same reasons you stated as well as my beneficial colonies.
I decided to go with the calcium carbonate because I couldn’t find any complaints with the use of calimagic and coco (derived from calcium carbonate) and they don’t seem to mind minus the crazy stretching. Because of that, I’ve tweaked the formula, I’m running 321 with 20 % less CalNit and compensating with 70 ppm of my Calcium carbonate.
For peace of mind, I fill my head with information about my stressors, which is how I ended up here, trying to find a better source of cal.
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Check this out. I see nitrogen, maybe I’m not understanding how things tie together.
There also seems to be a pinch of chlorine in there, says max .1%.
Just wanted to give a bit back
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It’s listed as a fertilizer, so I’d think if it provides nitrogen, it would have to be listed. Maybe it’s not in a useable form by the plant.
Use this product to suplement the calcium in your nutrient solution that is supplied by calcium nitrate. One gram of RexolinE-Ca-10 per gallon final volume nutrient solution provides approximately 25ppm calcium and 32 ppm Sodium.
Can Not be mixed into concentrated stock solutions with other calcium containing salts, ie calcium nitrate or calcium chloride
Seems like it only provides calcium and sodium?
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Very well could be. I’ll be emailing them and if I hear back I’ll post the response.
Thank you for sharing your knowledge. I appreciate it
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I appreciate the heads up. Now I want to get to the bottom of it too! Let me know if you get an insightful response. 
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Hey buddy been a long time. Found this thread again due to issues with my K:Ca:Mg ratio and it looks like you are still at it.
I always get this issue mid to late flower. Will read what I’ve missed since I last visited
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Have you been using this with any success? If so at what rates?
I have been using it. I’m currently using the Rev2 schedule in the May 28th post. There’s EC listed there… you can follow it roughly, but dilute it to what your plants want. I’ve used it for 2 grows now, with no plans to change. I haven’t had any calcium deficiency.
The reason you are getting calcium deficiency is because your Ca needs to increase as your K increases. K is antagonistic toward Ca uptake, so it’s important to keep the correct ratio between them. It’s very easy to get calcium deficiency in coco. You should not let your Ca ppms drop below one half of your K ppms. I think a ratio of 1.8 K:Ca is good. Bloom boosters are no bueno in coco, because it already has an abundance of K. Bloom boosters will cause Ca deficiency.
The difficulty is that boosting K in flower is difficult for coco due to the medium’s high affinity for Ca ions. Ca leaches out of your feed, and attaches to the coco, releasing more K. Ca is difficult to get without increasing N, which is also a problem for late flower. My solution has been to use Calcium EDTA to supplement Ca, instead of cal nitrate. Seems to be pretty effective, and doesn’t require using too much.
The rates are very roughly per gallon, but I generally just dilute to the proper EC. The flower formulas will produce about ~1.8 EC if you apply the amounts per gallon. Veg formulas can give ~2-3 gallons to get lower EC, up to ~1 gallon for the higher veg EC.
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I’m in RDWC with a 70gal system doing biweekly res changes so was just trying to get a gauge for how much I would be going through
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Ah ok. In that case you might be just fine with the normal 321 formula. But if you’re getting Ca deficiency in late flower, still consider that if you’re using bloom boosters, they’re probably the culprit. I’m using this formula with DTW in coco… so I’m using a lot of it. DTW gets expensive pretty quick if you don’t buy the salts in bulk… and that’s the whole reason I’ve been busting my ass researching this shit lol.
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My culprits are lights too close or Ca deficiency.
When I did my res change two weeks ago is when I noticed problems and they haven’t grown closer to the lights in that time which is why I’m leaning more towards calcium.
I don’t have much experience with light stress, but it sounds like something that wouldn’t gradually develop over time unless the plant is growing closer to the light in that time.
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Great thread, @lefthandseeds
New to site. I’ve been doing some busting myself on nute knowledge.
I’m a Coco grower, currently using Jacks 321ish. Have used GH and MegaCrop also.
Don’t wanna spam up your post.
Sure would like to have your input on my nute mix, check my thread “Coco Cavern” thread.
Thanks and happy growin.
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Yeah, no problema. I’ll have a look!
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A few updates here.
After a few grows with Calcium EDTA, I think I’ve decided against it. The biggest reason is that I re-read the product label and it provides sodium in greater parts than Calcium even. Adding sodium is no bueno for coco, and more fussy plants seem to show calcium deficiency. I think it’s an antagonist toward other 2+ ions (Ca, Mg), so I’m not certain it’s worth using. I’ve read on forums for other plants that it’s only recommended for foliar application, which is making sense to me.
As an alternative, I have some amino acid chelates that I was messing with a little while ago. I’ll post a v3 recipe with Calcium Gluconate and Magnesium Glycinate pretty soon. I’m going to re-balance the K:Ca ratio to be a little lower, maybe from 2 to 1.8 or 1.6. Veg/transition formulas are perfect as-is. Especially happy with the veg.
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Have you tried making your own calcium from egg shells and vinegar?
I have some that I made, but I’m unsure of its actual Ca content and appropriate dosage…
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