Essential foundation of our 4-part hydroponic system. Premium chelated calcium, magnesium, and iron can significantly reduce deficiencies and strengthen plants from seed to harvest. Save substantially vs. liquid Cal-Mag.
3.2% calcium, 1.2% magnesium, and 0.1% chelated iron in a single formula designed to address the most common hydroponic deficiencies.
Dissolves rapidly with minimal residue—safe for drip emitters, aeroponic misters, and recirculating NFT systems.
Concentrated powder ships nutrients, not water. One 5 lb bag can replace multiple gallons of liquid Cal-Mag at a fraction of the cost.
Can significantly reduce the risk of blossom-end rot, tip burn, and interveinal chlorosis—consistent use makes prevention far more manageable than correction.
EDTA-chelated iron remains plant-available at pH 5.0–6.5, helping prevent new growth yellowing common in hydroponic systems. Maintain pH 5.8–6.2 for best iron uptake.
Long shelf life when stored sealed and dry—far less waste compared to liquid products with fixed expiration dates.
Coco naturally binds calcium, making deficiency very likely even with tap water. Cal-Mag every watering helps prevent cation exchange lockout.
Significantly less shipping weight than liquid alternatives reduces carbon emissions and packaging waste.
Third-party lab tested for purity and heavy metal content, with results consistently well below required limits. CDFA registered to meet California's strict agricultural standards.
Designed as the first component added to water in our complete hydroponic feeding system—Cal-Mag, Grow, Micro, and Bloom.
Cal-Mag Plus uses pharmaceutical-grade mineral sources selected for maximum solubility and immediate plant availability. No chlorides, no fillers.
Fast-acting, fully soluble calcium source that also provides nitrate nitrogen for immediate uptake.
Highly soluble magnesium essential for chlorophyll production and photosynthesis efficiency.
Cal-Mag Plus provides the essential secondary nutrients that base fertilizers lack. The 2% nitrogen comes from nitrate sources for immediate plant availability, while calcium, magnesium, and chelated iron address the three most common hydroponic deficiencies.
Low nitrogen from nitrate sources provides immediate availability without competing with the primary base fertilizer's nitrogen delivery.
Calcium is essential for cell wall integrity and may help reduce the risk of blossom-end rot, tip burn, and structural weakness—particularly during rapid growth phases when demand spikes.
Central atom in every chlorophyll molecule. Deficiency causes interveinal chlorosis—yellowing between veins on older leaves that moves upward.
EDTA chelation keeps iron plant-available at pH 5.0–6.5. Maintain nutrient solution at 5.8–6.2 to prevent new growth yellowing; EDTA stability decreases above 6.5.
Reverse osmosis and distilled water start at 0 EC with zero minerals. Cal-Mag replaces what purification removes before adding base nutrients.
Coco coir's cation exchange sites bind calcium and magnesium, releasing sodium and potassium instead. Without consistent Cal-Mag supplementation, calcium and magnesium deficiency is very likely—even with calcium-rich tap water.
High-intensity indoor environments can increase calcium demand and expose delivery limitations, especially during rapid growth. Growers using high-output LEDs often find increasing Cal-Mag by 25% helps maintain adequate calcium levels.
Cal-Mag Plus is the foundation of our 4-part system. Always add it FIRST to your water before any other nutrients to help prevent precipitation.
| Package Size | Water Needed | Concentration | Yield |
|---|---|---|---|
| 2.5 lbs | 1 gallon | 2.5 lb/gal | 1 gal concentrate |
| 5 lbs | 2 gallons | 2.5 lb/gal | 2 gal concentrate |
| 10 lbs | 4 gallons | 2.5 lb/gal | 4 gal concentrate |
| 25 lbs | 10 gallons | 2.5 lb/gal | 10 gal concentrate |
| Water Type | EC Reading | Cal-Mag Rate | Notes |
|---|---|---|---|
| RO/Distilled | 0.0 | 100% (10 ml/gal) | Always required |
| Soft Tap | 0.1–0.3 | 75% (7.5 ml/gal) | Monitor monthly |
| Medium Tap | 0.3–0.5 | 50% (5 ml/gal) | Check water report |
| Hard Tap | >0.5 | 25% or skip | May have enough Ca/Mg |
| Growth Stage | Cal-Mag Plus 2-0-0 |
Grow Green 4-2-6 |
Micro Green 2-0-3 |
Blossom Green 2-6-8 |
EC Target |
|---|---|---|---|---|---|
| Seedlings | 2.5 | 1.25 | 1.25 | 1.25 | 0.5–0.8 |
| Early Veg | 5 | 5 | 5 | 5 | 1.0–1.4 |
| Late Veg | 7.5 | 15 | 10 | 5 | 1.4–1.8 |
| Transition | 10 | 10 | 10 | 10 | 1.6–2.0 |
| Early Bloom | 10 | 5 | 10 | 15 | 1.8–2.2 |
| Peak Bloom | 10 | 0 | 10 | 20 | 2.0–2.5 |
| Late/Flush | 5 | 0 | 7.5 | 15 | 1.5–2.0 |
| Symptom | Deficiency | Solution |
|---|---|---|
| Blossom-end rot | Calcium delivery | Check pH (6.0–6.5), EC, irrigation consistency, and root health first; consider increasing to 15 ml/gal if calcium supply is confirmed low |
| Yellow between veins | Magnesium | Foliar spray 5 ml/gal |
| Brown leaf tips or tip burn | Possible calcium stress or excess salts | Check EC, pH, irrigation consistency, and root health first; target pH 6.0–6.5 for calcium uptake |
| New growth yellowing | Iron | Lower pH to 5.8; EDTA iron availability decreases above 6.5 |
Always add Cal-Mag to your reservoir first, then stir before adding other nutrients. Calcium can precipitate (form white solids) when it contacts concentrated sulfates or phosphates directly. Diluting Cal-Mag into the reservoir first substantially reduces this risk. For unfamiliar nutrient combinations, a jar test before reservoir mixing is always recommended.
| Feature | Cal-Mag Plus 2-0-0 | Liquid Cal-Mag | CalMag Pro |
|---|---|---|---|
| Form | Dry Powder | Liquid | Liquid |
| Ca-Mg-Fe | 3.2-1.2-0.1 | 2-0.5-0.1 | 3-1-0 |
| Shelf Life | Indefinite | 2 years | 3 years |
| Cost per gallon | $0.08 | $0.25 | $0.20 |
| Shipping Weight | Much less | Heavy | Heavy |
| System Design | 4-Part Complete | Supplement | Supplement |
Competitor specifications are approximate and subject to change. Verify current labels before purchasing.
Refer to the Safety Data Sheet (SDS) in the Documents section for complete safety information.
Cal-Mag Plus works best as part of our complete 4-part hydroponic nutrient system. Each component is designed to work together for balanced nutrition from seed to harvest.
Vegetative growth formula with balanced NPK for lush, healthy foliage during veg stage.
EssentialFlowering formula with high phosphorus and potassium for abundant blooms and fruit development.
EssentialComplete micronutrient package with chelated trace elements for enzyme function and plant health.
Best ValueGet all four components together and save. Everything you need for a complete hydroponic feeding program.
Powder costs significantly less per dose, ships with much less weight, never expires when stored dry, takes less storage space, and lets you adjust concentration based on your water quality. You pay for nutrients, not water.
It depends on your water hardness. Test your water EC: below 0.3 EC needs Cal-Mag, while hard water above 0.5 EC may already contain enough calcium and magnesium. Get a water report from your utility for exact levels. For more on nutrient management, see our Complete Hydroponic Nutrient Guide.
Yes. Mix 5 ml of stock solution per gallon and spray in the early morning or late afternoon to reduce evaporation and leaf burn risk. Foliar feeding provides rapid correction of visible deficiencies. Avoid spraying during peak midday heat and stop foliar applications 2 weeks before harvest.
Strongly recommended. Coco coir's cation exchange sites naturally bind calcium and release sodium in its place, making deficiency very likely even with calcium-rich tap water. Use Cal-Mag every watering at 5–7.5 ml/gal and pre-buffer new coco with 10 ml/gal solution. Learn more in our Coco Coir Growing Tips & Best Practices article.
Calcium deficiency shows as blossom-end rot, brown spots, and tip burn. Magnesium deficiency causes yellowing between leaf veins on older leaves. Iron deficiency appears as yellowing of new growth. Prevention is always easier than correction. For help identifying symptoms, see Understanding Calcium & Magnesium Deficiencies.
Calcium can precipitate (form white insoluble solids) when mixed directly with concentrated sulfates or phosphates. Adding Cal-Mag to water first dilutes it sufficiently so that when you add subsequent nutrients, concentrations are much less likely to reach precipitation thresholds. For unfamiliar combinations, a jar test before mixing in the main reservoir is always a good practice.
A properly stored stock solution in a sealed container lasts 2–4 weeks. If you see any cloudiness or precipitate forming, discard and make a fresh batch. The dry powder itself has an indefinite shelf life when kept sealed and dry.
Not completely satisfied? Return within 90 days for a full refund. We stand behind every product we sell.
Our team of horticulture experts is available Monday–Friday to help you get the best results. Email us at questions@greenwaybiotech.com for personalized growing advice.
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