Best Coco Coir for Hydroponic Growing
Coco coir behaves like soil but feeds like hydro — it holds water and air at the same time, and it's inert, so you control every nutrient the plant sees. The catch is that raw coco is loaded with sodium and potassium and will lock out calcium and magnesium until it's buffered. Buy RHP-certified, pre-buffered coco and that problem disappears; buy cheap unwashed coco and you'll fight it all cycle. Below is what we stock, from single bricks to full pallets.
How to choose coco coir
- RHP certification is the meaningful quality mark — washed, buffered, and tested for EC and sodium.
- EC of the raw product should be under 0.5 mS/cm. Higher means salt you'll have to flush out.
- Coco vs coco-perlite blends. 70/30 coco-perlite drains faster and suits frequent fertigation. Straight coco holds more water and suits hand watering.
- Form factor. Compressed bricks are cheapest per litre and store small. Loose bags are ready to use. Coco cubes and open or closed-top bags suit drip systems.
- Chips vs pith. Chunky chips add air; fine pith holds water. Most quality products are a blend.
Running coco correctly
| Variable | Target |
|---|---|
| pH (in and out) | 5.8–6.2 |
| EC (feed) | 0.8–2.2 depending on stage |
| Cal-Mag | Required from day one |
| Runoff | 10–20% every feed |
| Feed frequency | Daily minimum; 2–5× daily under drip |
Coco holds calcium and magnesium poorly because its cation exchange sites preferentially bind potassium and sodium. That's why Cal-Mag is mandatory in coco and optional in soil. It isn't an upsell, it's chemistry.
What to skip
- Unwashed, uncertified coco. The money you save goes straight into Cal-Mag and flushing.
- Letting coco dry out fully between waterings. Dry coco is hard to re-wet evenly, and EC spikes as it dries.
- Treating coco like soil and watering every three days. It wants daily.
Frequently asked questions
Do I need to buffer coco coir?
If it's RHP-certified and sold pre-buffered, no. If it's raw or uncertified, yes — soak it in a Cal-Mag solution before use.
Why do I need Cal-Mag with coco?
Coco's exchange sites bind potassium and sodium in preference to calcium and magnesium, so those get locked out unless you supply extra.
What pH for coco coir?
5.8–6.2 going in and coming out. It's a tighter window than soil and closer to hydroponics.
Coco or coco-perlite?
Straight coco if you hand water. 70/30 coco-perlite if you're running drip or fertigating several times a day.
Related
All growing media · pH meters and testing · Pots and containers · Nutrients and Cal-Mag
