Grotek Cal-Max: the calcium and magnesium your water doesn’t provide
Perfectly pure reverse-osmosis water, coco coir that locks up calcium, growth so fast the plant can’t keep up… In every one of these cases, the same deficiencies eventually show up. Cal-Max from Grotek brings together in one bottle the elements most often missing: calcium, magnesium, nitrogen and chelated iron.
When to use Cal-Max
- With reverse-osmosis or distilled water: it contains almost no calcium or magnesium. Cal-Max puts them back.
- In coco coir: coco tends to hold on to calcium. Use Cal-Max to prepare the medium before planting and throughout the grow.
- During fast growth or high heat and humidity: plants can struggle to take up enough calcium.
- To correct a minor deficiency, as a root feed or as a foliar spray for faster action.
Specifications
| Brand | Grotek (Canada) |
| Type | Calcium, magnesium and iron supplement |
| Composition | 2% nitrogen, 3% calcium, 1% magnesium, 0.1% chelated iron (EDTA) |
| Phase | Growth and flowering |
| Application | Root feed and foliar spray |
| Growing media | Soil, coco, peat and hydroponics |
| Sizes | 1 L, 4 L and 10 L |
Dosage and directions
| Use | Dose |
|---|---|
| Soil and coco (root feed) | 5 ml per 4 litres (about 1.25 ml/L) |
| Hydroponics | 5 to 8 ml per 4 litres (1.25 to 2 ml/L) |
| Foliar spray | 10 ml per 4 litres (2.5 ml/L) |
| RO water | Add Cal-Max up to an EC of 0.4–0.6 mS/cm before your nutrients |
For foliar use, spray both sides of the leaves in low light, just before lights-off, and never onto flowers. Before raising the dose, also check pH and watering: not every yellow leaf is a deficiency.
In your Grotek programme
Cal-Max complements your base nutrient, such as Grotek Solo-Tek Grow. In hydro and coco, pair it with Grotek Pro-Silicate for sturdier stems and Grotek Vitamax Plus for vitamins. Browse the full range in our Grotek nutrients category.
FAQ
Cal-Max or CalMag: what’s the difference?
They are the same type of product: a calcium and magnesium supplement. Cal-Max is Grotek’s version, with added nitrogen and chelated iron.
Do I need it with tap water?
Not necessarily: hard water already contains calcium and magnesium. Cal-Max is most useful with soft or RO water, or in coco coir.
Can I mix it with organic nutrients?
Cal-Max is a mineral supplement and works with most programmes. Add it to the water, stir, then check the pH.
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