CalMag for Coco and RO Water: What It Does and How to Use It
Calcium and magnesium are essential for healthy plants. Calcium plays a part in building cells and magnesium is at the heart of photosynthesis. Many growers find they need to add extra of both, especially when growing in coco or using soft tap water or reverse osmosis (RO) water.
Why soft water, RO water and coco need extra
- Soft and RO water contain little calcium and magnesium, so the plants have to get them from your feed.
- Coco tends to hold on to calcium, which is why most coco growers add a CalMag supplement throughout the crop.
Signs your plants may be short
- Calcium: distorted or stunted new growth and brown, crispy leaf tips or edges.
- Magnesium: yellowing between the veins, usually starting on older leaves.
These signs can have other causes, such as pH or EC being off, so check those first before changing your feed.
How CalMag supplements are used
Dosing differs between brands, so always follow the label. As an example, BioBizz CalMag is dosed at 0.5 to 1.5ml per litre, and 1ml per litre raises the EC by about 0.1. CANNA CalMag Agent is made to raise the calcium and magnesium content of soft water, which also raises its EC.
When treating RO or soft water, the usual order is:
- Fill your tank with water.
- Add the CalMag first and measure the EC until you reach the level you want.
- Add your base nutrients and additives.
- Check and adjust the pH last.
For coco, many feeds recommend a pH of around 6.0, but check the instructions on the nutrient you use.
CalMag supplements we stock
We stock CalMag products from BioBizz, CANNA, Mills, Dutch Pro, Athena, Plant Magic and Shogun. Browse the range in our nutrients collection, or see our coco coir and measuring tools. Not sure which suits your water? Call 01744 382 066 or visit us in Rainford.