Roots Organics CalMag – 2.5 Gallon

Roots Organics CalMag is a pure, all-natural blend of calcium, magnesium, and sulfur formulated to support plants through fast growth and heavy feeding phases. Unlike many CalMag products, it contains no added nitrogen, phosphate, or potassium — so you can correct secondary nutrient deficiencies without shifting the primary fertility ratios you have dialed in. Designed to work alongside high-quality base fertilizers, this 2.5-gallon container provides enough concentrate for extended commercial production cycles.

Roots Organics CalMag Specifications

Specification	Value
Brand	Roots Organics
Container Size	2.5 Gallon (approx. 9.46 L)
Shipping Weight	29.03 lb
Active Nutrients	Calcium, Magnesium, Sulfur
N-P-K Added	None (no added nitrogen, phosphate, or potassium)
Derived From	Kieserite, Gypsum
Formulation Type	Liquid concentrate
Supplier SKU	ROCM2.5G

Why Choose Roots Organics CalMag

Many growers encounter calcium or magnesium shortfalls when running high-performance plant programs, especially under LED lighting or in coco coir and other low-CEC substrates. Standard CalMag products often include nitrogen as part of their formula, which creates a problem: correcting Ca/Mg deficiencies with them means unintentionally adding more nitrogen than your feeding program calls for. Roots Organics CalMag avoids this by providing calcium, magnesium, and sulfur without any added primary nutrients.

The mineral sources — Kieserite and Gypsum — are well-established natural inputs. Kieserite (magnesium sulfate) delivers both magnesium and sulfur in a plant-available form. Gypsum (calcium sulfate) supplies calcium alongside additional sulfur. The result is a formula that addresses the most common secondary macronutrient gaps without requiring you to rebalance your entire feeding schedule.

Roots Organics designed this product to pair directly with their Buddha Grow and Buddha Bloom base fertilizers, but it works equally well alongside other complete base nutrients in soil, coco, and hydroponic systems. The 2.5-gallon size provides a large enough supply for commercial-scale applications while remaining manageable on a bench or in a mixing area.

• Delivers calcium, magnesium, and sulfur without altering N-P-K input ratios
• Derived from Kieserite and Gypsum — natural, mineral-based sources
• N-P-K free: no added nitrogen, phosphate, or potassium
• Formulated for fast-growing, heavy-feeding plant varieties
• Pairs with Roots Organics Buddha Grow and Buddha Bloom base fertilizers

Best Uses for Roots Organics CalMag

Roots Organics CalMag is most useful in situations where secondary nutrient deficiencies arise independently of primary nutrient levels. Here are the growing scenarios where it fits best:

• Coco coir and peat-based media: These substrates have a low cation exchange capacity and do not retain calcium or magnesium well, making supplementation a routine requirement in most feeding programs.
• LED-lit environments: LED fixtures drive faster growth rates and higher transpiration, which increases the plant’s demand for calcium and magnesium. Growers using high-intensity LEDs often need more CalMag than those running HPS.
• Soft water or RO-filtered water systems: Reverse osmosis and soft water sources strip out naturally occurring calcium and magnesium. Using CalMag in these setups replenishes what the base water is missing before fertilizers are added.
• Fast-growing, heavy-feeding crops: Plants with rapid vegetative growth or dense fruiting loads pull heavily on secondary macronutrients. CalMag keeps up with demand during peak growth phases.
• Correcting interveinal chlorosis or tip curl: Visual symptoms of magnesium or calcium deficiency — such as yellowing between leaf veins or marginal leaf curl — respond to targeted CalMag supplementation when the base nutrient program is otherwise on track.

If you are running a roots-health and microbial program alongside your base nutrients, Advanced Nutrients Tarantula is another additive in the Nutrients & Additives category that supports root zone development alongside secondary nutrient supplementation.

Compatibility

Roots Organics CalMag is a liquid concentrate compatible with the following systems and media types:

• Growing media: Coco coir, peat-based mixes, rockwool, perlite, and composted soil blends. Particularly useful in low-CEC media where calcium and magnesium leach out between feedings.
• Irrigation systems: Compatible with reservoir-based hydroponic systems, drip systems, ebb-and-flow tables, and hand-watered containers. Always add to water before adjusting pH.
• Base fertilizer programs: Designed to supplement Roots Organics Buddha Grow and Buddha Bloom. Also compatible with third-party base nutrients where no CalMag is included or where Ca/Mg levels are insufficient for the crop.
• Water sources: Most effective when used with reverse osmosis water, soft water, or any source with low baseline Ca/Mg mineral content. In hard water regions, test water hardness first — supplementation may not be needed.

Because CalMag contains no added nitrogen, phosphate, or potassium, it does not interfere with the primary nutrient ratios in any base fertilizer program. It can be added to an existing feed chart without recalculating N-P-K targets. If you are looking for a carbon-based additive to support microbial life and plant energy alongside your CalMag program, Earth Juice Hi-Brix Molasses is a complementary product in the same category.

Usage Guidelines

Because no application rate is listed in the canonical product data for this SKU, the following guidance reflects standard industry practice for liquid CalMag concentrates of this type. Always consult the product label for the manufacturer’s current recommended rates.

General dosing approach: Liquid CalMag concentrates are typically added to the reservoir or watering can before other nutrients. The reason is that calcium ions can react with sulfate or phosphate ions in concentrated nutrient solutions, so adding CalMag to plain water first and mixing thoroughly prevents precipitation.

1. Start with plain, pH-unadjusted water in the reservoir or mixing container.
2. Add Roots Organics CalMag at the rate specified on the product label, typically measured in mL per gallon or mL per liter.
3. Stir or circulate to mix thoroughly before adding base nutrients.
4. Add remaining nutrients in sequence per your feed chart.
5. Adjust pH to the appropriate range for your growing medium (5.5–6.5 for most hydroponic and coco applications; 6.0–7.0 for soil).
6. Measure EC to confirm the addition is within your target range for the growth stage.
7. Monitor plants for symptom resolution over 5–10 days; adjust dose at the next feeding if needed.

When correcting an active deficiency, some growers increase the CalMag dose temporarily until symptoms stabilize, then return to a maintenance rate. Avoid excessive application — over-supplementing calcium can antagonize potassium and magnesium uptake.

For growers running organic or biologically active programs, Down to Earth Crab Meal is a dry amendment that can further build calcium reserves in the root zone when used in soil-based systems.

How to Add CalMag to Your Feed Program

1. Assess your water baseline: Run a water test or consult your municipal water report to determine existing calcium and magnesium levels. RO and soft water typically read near 0 ppm for both; well water and tap water vary widely.
2. Identify deficiency or prevention need: Look for interveinal chlorosis (magnesium deficiency) or brown leaf-tip burn (calcium deficiency). Even without visible symptoms, coco and RO-water grows commonly require CalMag as a preventive measure.
3. Shake the bottle thoroughly: Settle may occur in concentrated liquid supplements. Invert or shake before measuring.
4. Measure into plain water first: Use a calibrated syringe or measuring cup. Add to the reservoir or mixing vessel before any other nutrients.
5. Add base fertilizer and remaining additives: Follow your normal nutrient-addition sequence after CalMag is fully dissolved.
6. Adjust and confirm EC and pH: Confirm that CalMag has raised EC as expected and that total EC remains within your target range. Adjust pH to the appropriate window for your medium.
7. Log and track: Record the dose and plant response. If deficiency symptoms persist after 7–10 days, consider a small increase at the next feeding cycle. If symptoms worsen or new antagonism appears, reduce dose and reassess.

Sources & Further Reading