Finally, an

Prevents common deficiencies.

CALMAG OAC | Organic

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Organic CalMag OAC is a groundbreaking calcium and magnesium supplement registered with the WSDA. It features an organic acid chelate that immediately drives calcium and magnesium inside of plant cells, and allows for these critical elements to be used for growth and photosynthesis.

Organic CalMag OAC enhances flower quality by providing forms of calcium and magnesium that are soluble across cell walls and immediately useful for plant growth, CalMag OAC can invigorate terpene and trichome synthesis, resulting in maximum productivity and yield.

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Prevent common deficiencies.

I grew several varieties and only the San Marzano and Roma tomatoes were presenting blossom end rot (BER). I used this once per week for 2 weeks and it all new fruit did not have BER. My new garden staple.


I'm growing 2 strains that are extremely sensitive to nitrogen excess and needed to supplement with some CalMag. This was the only product I could find that didn't have any nitrogen.

Mike T

Very strong, organic Cal Mag product. Very low usage. Don't overdo! A great company with great products at great prices. Try their great, organic Silica Gold product. Best I've used!

Tim T

I realize people use this for hydroponics, but this stuff is great in the garden. It's complimentary to other organic fertilizers. A tiny amount is more than enough.


I absolutely love this cal-mag product. I use coco and RO water and while I supplement with this product I have never had a cal-mag deficiency. Or any deficiency for that matter with the TPS Nutrient line.


I use this as a foliar spray and my plants love it. My favorite brand for my peppers that need nutrients from time to time.

Brennan K

Complimentary Nutrients

Frequently Asked Questions

CalMag OAC is an organic solution that has such a wide and balanced array of minerals that it really does a great job at aiding in healthy growth and preventing deficiencies.

You can use this nutrient from cutting or seedling through harvest.

We start with a highly pure and organic source of magnesium and calcium. We then micro-chelate it with organic acids and a plant extract package. The result is the most bioavailable CalMag in the gardening and hydroponic industry. One example of this is that when this CalMag is used in soil it is 10+ times more effective at uptake than nitrate calmags.

No, CalMag OAC is not a salt based CalMag and is not great at buffering. For buffering, please use our CalMag Complete.

Yes, for compost tea, add 5-10mL per gallon.

Yes there is iron, as well as an array of other micros. The NPK is 0-0-0 and the mineral breakdown is as follows: Nitrogen: 0% Calcium: 4.5% Magnesium: 1.1% Boron: 0.005% Copper: 0.007% Iron: 0.01% Manganese: 0.01% Sulfur: 0.05% Zinc: 0.01%

No animals at all, it is vegan. We make it from minerals, plants, microbially digested carbohydrates, and cretaceous shale.

Yes, you can use CalMag OAC for orchids. Just be sure to start with the lowest dosage rate that recommended to get your plant acclimated to the new nutrient. You can increase from there as you see needed. CalMag OAC is also great as an orchid foliar spray, try 10-20mL per gallon.

A shake before use is a great idea, though not required. The amino acids from the plant extracts in CalMag OAC can bind up over time. If you give it a shake they should reintegrate into he solution. If you mix feed water with the aminos stuck together, it's not a problem. The vigor of watering and mixing your feed water will disperse the aminos again.

CalMag OAC is organic and doesn't have nitrate salts - unlike many other non-organic calmags. OAC is made with organic acid chelates of Calcium and Magnesium. CalMag OAC should register on your PPM meter but at a much lower level than nitrate calmags, in general you can expect 45PPM per mL.

Yes, we recommend 10-20mL per gallon as a foliar spray. It's best to spray in the late afternoon and early evenings for optimal uptake.

Yes - however it is generally unnecessary to add additional CalMag to TPS One. If you have very hungry plants that require a lot of CalMag then we recommend using 1/2 dose of CalMag OAC to supplement.

CalMag OAC is guaranteed for 18 months from date of purchase, though it doesn't really expire. We recommend shaking up older bottles before use to mix the amino acids back into solution.

CalMag OAC contains no nitrogen and is an organic non-nitrogen version. CalMag Complete contains nitrogen and is partially organic and partially inorganic. Many growers will use CalMag Complete in veg and early bloom, and switch to OAC for bloom.

Bioavailability for CalMag OAC is fairly immediate for Calcium and Magnesium. We chelate with organic acids so it is in forms that plants and microbes love. Please make sure to follow the use rates - OAC is very strong and doesn't need to be over fertilized like some other organics.

Absolutely, a great way to get bioavailable Calcium, Magnesium, and micronutrients into the soil. To make it easy for these plants in soil, you can feed at 1-2tsp per gallon of feed water once weekly. Also, you can foliar spray in addition to watering in the soil. The feed rate for foliar is 10-20mL per gallon and you can spray once weekly.

Yes, CalMag OAC is nitrogen free - you can use it until the very end of your bloom. There are some amino acids in our plant extracts which contain nitrogen, however it is minimal and would equate to approximately .01%.

It sure will. Check out our feed charts for the TPS Component Series, including Organic CalMag OAC. There you'll find a hydro/DWC feed chart specifically for your style of feeding and your plant type.