• Wear gloves and eye protection when handling powder
• Avoid inhaling dust—use in well-ventilated areas or wear a dust mask
• Wash hands thoroughly after handling

• Store in a cool, dry place in the original sealed container
• Hygroscopic—absorbs moisture from air. Reseal tightly after each use
• Keep out of direct sunlight and away from heat sources
• Keep away from children and pets

• Always add Cal-Mag to water FIRST before other nutrients to help prevent precipitation
• Never mix concentrated Cal-Mag directly with concentrated sulfate or phosphate fertilizers
• Dissolve in warm water for fastest results—do not use boiling water
• Avoid contact with metal surfaces—rinse equipment after use

• Eye contact: Flush with clean water for 15 minutes. Seek medical attention if irritation persists
• Skin contact: Wash affected area with soap and water
• Ingestion: Do not induce vomiting. Contact Poison Control (1-800-222-1222) or seek medical attention
• Inhalation: Move to fresh air. Seek medical attention if symptoms persist

Refer to the Safety Data Sheet (SDS) in the Documents section for complete safety information.

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.

• Third-party lab tested for purity and heavy metal content, with results consistently well below required limits
• CDFA registered—meets California's strict agricultural standards
• Family-owned and operated for 35+ years, manufacturing in Madera, California since 1989
• Widely used by hydroponic growers across the US and internationally
• Long shelf life when stored sealed, dry, and free from contamination

Not completely satisfied? Return within 90 days for a full refund. We stand behind every product we sell.

• Concentrated powder significantly reduces shipping weight compared to liquids
• Less packaging waste per nutrient delivered
• No water shipped—mix fresh when you need it

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.