Product Information
About CalMag & Iron
Give your garden exactly what it needs with our cal mag nutrients for hydroponics. This formula is specifically designed to come to the rescue of any plant with deficiencies that may be present. CalMag & Iron is a liquid calcium, magnesium, and iron supplement for plants that will not only treat a deficiency but support the growth and development of your garden.
CalMag & Iron works especially well in soil, hydroponic, and container gardens, ensuring strong and healthy yields in both. We also recommend using this formula on plants growing in coco substrate or reverse osmosis water because the absorption process becomes magnified in these conditions.
Many flowering varieties need this type of blend to flourish properly.
Order your Cal Mag & Iron today!

CalMag & Iron Feed Chart

Mixing Procedure
1) Fill your reservoir with water. It may be filtered or tap water. If you use filtered water you may need to add some CalMag & Iron.
2) Add HUMBOLDTS SECRET NUTRIENTS listed on the feed chart (Shake each bottle a little bit)
3) After you add your nutrients, adjust the PH so that your end mixture in your reservoir is between 5.5 and 6.5 (If needed.)
4) Can be used in Soil, Coco, Deep Water Culture (DWC) and Aeroponics. Typically less nutrients are used in DWC. If you grow in Hydroponics it is recommended that you use Golden Tree at a lower dose and use Plant Enzymes. We suggest you play around with the amounts of each nutrient and find out what works best for your setup as there are many variations to growing.
Additional Information
1) In order to have a successful grow growers should use at minimum Base A, Base B & Golden Tree.
2) For Veg: Add 1-2ml of Golden Tree per gallon to your reservoir. Then, add your base nutrient until PPM levels of the reservoir mixture reaches between 800-1000 (Hanna Scale)
For Flower: Add 2-5ml of Golden Tree, then add base nutrient into your reservoir until your PPM levels of the reservoir mixture reaches between 1000-1300 (Hanna Scale, which is 2.0-2.6 in EC.) Remember that this is a rough estimate. Strains and growing mediums vary, some will enjoy higher PPM's and some lower. Flushing at the end is not necessary.
Shake bottle and measure out 3-5mL per gallon of water
Shake bottle and measure out 3-5mL per gallon of water
Apply to the root zone, or use as a foliar spray. For optimal results feed with every watering as needed throughout your entire growing season.

We are confident that you will be pleased with your product and offer a 6 month 100% satisfaction guarantee.
Refer to our return policy for full terms for the satisfaction guarantee.
Frequently Asked Questions
Yes!
Humboldts Secret CalMag & Iron can be used as both a soil drench and foliar spray.
Coco coir naturally draws on calcium and magnesium making it unavailable to plants. By using Humboldts Secret CalMag & Iron you can avoid any deficiencies before they happen.
CalMag & Iron help correct many common plant deficiencies, helps supplement calcium and magnesium for those using RO water, and helps increase nutrient absorption!
Customer Feedback
Don’t just take our word for it..
Rated by hundreds of happy growers
I used this with other nutes to help prevent know deficiencies in 'tomato plants'...I never experienced any of the symptoms that are common to these plants while using this product. Will buy again!
Humbolt's Secret appears to be doing a great job of keeping our roses healthy
Love the product. With just one application I started seeing positive results. Plants started to set buds and I also see new roots emerging. The vegetable garden is growing exuberanty. Have used other cal/ mag products but never saw immediate results like this
Great stuff, plants responding well, with no known deficiencies.
Grow bigger plants in less time without struggle

Get the Startaer Kit for only $170.77 $99.99
Each Starter Kit Includes:
- World's Best Base Nutrient System Grow & Bloom Base A and B (1/4 Gallon of Each)
- Golden Tree (1/8 Gallon)
- Flower Stacker (1/4 Gallon)
- CalMag & Iron (1/4 Gallon)
- Plant Enzymes (8 Ounces)