Bloom CAL-MAG Super Concentrate — Professional Calcium & Magnesium Supplement for Indoor Growing
Best for: Growers using soft water, RO systems, or coco coir who need to prevent secondary nutrient deficiencies without overcomplicating their feed
Our thoughts
If you're growing indoors with soft or filtered water, calcium and magnesium deficiencies will find you eventually. This is the practical fix — a professional-grade concentrate that integrates cleanly into any nutrient system without the drama. Simple, reliable, and made from organic-based ingredients that actually work.
Bloom CAL-MAG Super Concentrate is a liquid calcium and magnesium supplement designed to prevent and correct secondary nutrient deficiencies that plague indoor growers using soft water, reverse osmosis systems, or growing in coco coir. Formulated from organic-based ingredients with added chelated iron and zinc, it's a working supplement that does exactly what it should — keep your plants healthy without requiring you to redesign your entire nutrient programme.
Why calcium and magnesium matter
These aren't optional extras. Calcium strengthens cell walls and supports nutrient transport throughout the plant. Magnesium is the engine behind chlorophyll production — without enough, your plants lose photosynthetic power and growth stalls. In soft water areas (common across the UK), or when using RO and filtered water, you're starting from zero. Coco coir growers face the same problem because coco locks up these minerals differently to soil.
Early signs you need this: yellowing leaves, browning leaf edges, curling growth, or blossom end rot. But the smarter move is to prevent it happening in the first place.
How it compares
Bloom CAL-MAG sits in the professional-grade tier of secondary nutrient supplements.
- Professional formulation used by commercial growers — not a budget afterthought
- Includes chelated iron and zinc on top of calcium and magnesium (most basic cal-mag products don't)
- Organic-source ingredients, quality-checked by Advanced Floriculture on every batch
- Compatible with any growing medium (soil, coco, hydro) and any existing nutrient system
- Super concentrate format means a 1L bottle goes much further than standard formulations
Compared to powder alternatives, you get instant mixing and consistent dosing. Compared to budget liquid cal-mag, you're getting additional micronutrients and a brand that actually knows what they're doing.
Usage guidance
This is straightforward to use because it's designed to integrate into your existing feed, not replace it.
Dosing
Apply at 1ml per litre of water throughout vegetative growth and flowering phases. That's it. No complex calculations, no adjustments based on medium type — this dose works across soil, coco, and hydro systems.
Application timing
Use from early growth right through to the final week. Stop adding it during the last 1-2 weeks (your final flush), when you're running plain water to clear residual salts.
Water type matters
If you're on mains water, soft water supply, or using RO/distilled water, run this as part of your regular feed. If you're using tap water in a hard water area, you might not need it — but adding it won't hurt and gives you insurance against deficiencies.
Integration with your nutrients
Unlike some supplements that force you to reduce other nutrient doses, Bloom CAL-MAG works alongside your existing programme. You don't need to cut back on your primary feed to use this. Just add the 1ml/L dose on top of what you're already doing.
Hydroponic and drip systems
Works cleanly in automated systems. The concentrate stays soluble and won't clog lines or emitters when dosed correctly.
Technical specifications
- Calcium content: 5%
- Magnesium content: 1.4%
- Additional micronutrients: Chelated iron and chelated zinc
- Source ingredients: Organic-based formulation (calcium nitrate, magnesium nitrate, chelated iron and zinc)
- Application rate: 1ml per litre of water
- Format: Super concentrate liquid
- Available sizes: 300ml, 1L, 2.5L
- Growing medium compatibility: All media types — soil, coco coir, hydroponic systems
- Quality assurance: Every batch quality-checked by Advanced Floriculture. Colour and consistency may vary naturally due to organic sourcing — this is normal
Who this is for
- UK growers in soft water areas dealing with naturally low calcium and magnesium levels
- Anyone running RO, distilled, or filtered water systems and starting from zero nutrient baseline
- Coco coir growers (coco binds these minerals tightly, making supplementation essential)
- Hydroponic and drip system operators who need soluble, non-clogging supplements
- Growers who've seen yellowing leaves, browning edges, or stunted growth and want to prevent it happening again
- Experienced growers who already run a nutrient system and just need a reliable secondary nutrient solution
Particularly well suited to indoor growing setups where water quality control matters and consistency across multiple growing cycles is the priority.
Our take
This is professional-grade supplementation at a price that makes sense. The addition of chelated iron and zinc sets it apart from basic two-element cal-mag products, and the fact that it's made from organic-sourced ingredients without compromising mixing reliability is the kind of detail that separates actual growing supplements from supermarket shelf-fillers.
If you're using soft water, RO systems, or growing in coco, this isn't optional — it's the difference between healthy plants and nutrient-chase mode. Worth picking up while stock lasts. Does exactly what it should, day in, day out.
