The Coco Coir Quality Problem
Coco coir is made from the fibrous husk of coconuts, and coconut plants accumulate potassium and sodium from seawater in coastal growing regions. This salt remains in the fibre after harvest and processing unless specifically removed. Cheap, unbuffered coco coir releases this sodium and potassium into your nutrient solution, competing with calcium and magnesium uptake and causing deficiency symptoms even in well-formulated nutrient solutions.
Quality buffered coco is pre-washed to remove salts and pre-loaded with calcium and magnesium, so it does not rob your plants of these critical nutrients. The difference in plant performance between buffered and unbuffered coco is significant — and invisible unless you know what to look for.
How We Tested
We assessed each coco product on: initial EC and pH (should be EC <0.5, pH 5.5–6.5 from the bag), water retention and drainage characteristics, particle size consistency, salt content (measured after a standard water leach), and reusability after sterilisation. We grew three crops of basil in each media with a controlled nutrient solution to observe any media-related nutrient interference.
Buffered vs Unbuffered: The Test Results
Three of the six products tested showed significant calcium lockout symptoms within the first 2 weeks of growing when using standard hydroponic nutrients without Cal-Mag supplementation. The three RHP-certified, pre-buffered products (CANNA Coco Professional Plus, Plagron Cocos Premium, and Cyco Coco) showed no nutrient interference and maintained consistent pH throughout the grow cycle. Our recommendation is clear: always buy RHP-certified, pre-buffered coco coir for hydroponics.