HESI CalMag bottles in multiple sizes on a white background

HESI CalMag 250 ml bottle on a white background

HESI CalMag 500 ml bottle on a white background

HESI CalMag 1 L bottle on a white background

HESI CalMag 2.5 L bottle on a white background

HESI

HESI CalMag

Calcium + magnesium support
For soft, RO or demineralised water
Supplement only

Choose HESI CalMag when soft, filtered, distilled or RO water leaves plants short of calcium and magnesium. It is especially suitable in coco, semi-hydro and mineral feeding setups where tap-water minerals are missing. Use it to correct the water first, then add the main fertilizer.

Quick facts

Type: CalMag supplement
Substrates: Soil / potting mix, Coco, Hydro, Passive semi-hydro, and LECA
Dosage: 50 ml/10 L
Frequency: As needed for soft water
Skill level: Intermediate
pH/EC: Recommended

€7,25

VAT included · plus

Please note: Most fertilizers ship separately from plants. A separate shipping fee may apply, and the final cost is calculated at checkout by order weight. Free shipping does not apply.

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HESI CalMag supports the mineral side of a feeding plan when water or substrate conditions leave calcium and magnesium short. It is a correction tool, not a general weekly treat.

Balance before feeding

CalMag prepares the mineral background so the chosen base fertilizer can work more predictably. It is not a replacement for plant food and is not a universal weekly extra.

For controlled corrections

Reach for it when the setup points to a calcium or magnesium gap. For a straightforward feeding plan, start with a complete fertilizer and add CalMag only when the water or medium calls for it.

Is it right for your plant?

Substrate Soil / potting mixCocoHydroPassive semi-hydroLECA
Best for Foliage plantsCoco-grown plantsSemi-hydro plantsPlants under grow lights
Helps with Regular feedingMineral balanceWater correction
Choose another product for complete base feedinghard-water correction

HESI CalMag fits coco, hydro, semi-hydro and mineral soil feeding where calcium and magnesium run low. It is especially relevant for plants under strong grow lights or when filtered water is used.

Most ordinary hard tap-water setups will not need it at every watering.

What's inside:

NPK Ratio: NPK 5-0-0 + 7.5% MgO, 5.0% CaO, iron chelate and molybdenum
Nutrient basis: Mineral Ca/Mg/N supplement with iron chelate and molybdenum

HESI CalMag is a calcium-magnesium supplement with nitrogen and trace support. It is for water or substrate situations where the base feed needs mineral backup.

The composition is NPK 5-0-0 with 7.5% MgO, 5.0% CaO, iron chelate and molybdenum. Count the nitrogen contribution when combining it with another fertilizer.

How to use it

Use HESI CalMag it before the base fertilizer when starting with RO, distilled, demineralised or very soft tap water. Aim for a starting EC around 0.4-0.5; as a rough guide, RO water often needs about 3-4 ml per 5 L.

Once the water is corrected, add the main plant food and adjust the final solution as usual.

➜ A few notes before measuring, mixing or applying :

Check water hardness or EC before making it a permanent weekly addition. Too much CalMag can crowd out other nutrients, so treat deficiency correction as temporary.

Shake well and keep the bottle sealed to protect the chelated trace elements.

HESI CalMag

€7,25

Frequently Asked Questions about HESI CalMag

Do I need HESI CalMag for normal tap water?

Not always. It is most useful with RO, distilled, demineralised or very soft water, and in coco, hydro, semi-hydro or mineral feeding where calcium and magnesium can run low.

Is HESI CalMag a complete fertilizer?

No. It supplies calcium and magnesium, but it does not replace a balanced base fertilizer.

When should I add HESI CalMag?

Add it to the water before the base fertilizer, especially when correcting soft or RO water. Then add the main plant food and check the final solution.

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