pH and nutrient control

pH up, pH down and calibration for grow tents

Nutrients only become available to the plant within a fairly narrow pH window, so a feed that's perfectly mixed but sitting outside range is close to wasted. Coco and hydro growers should be aiming for pH 5.8 to 6.2 at the root zone; soil is more forgiving at 6.0 to 6.5. Check pH after mixing nutrients, not before — adding concentrate always shifts the reading, sometimes by half a point or more.

Canna pH Down is a bloom-specific acid concentrate that plays nicely with Canna's own base feeds; most pH down products work fine across brands as long as you dose gradually. Meters drift over time, which is why Growth Technology Buffer 4 and Buffer 7 calibration solutions matter — recalibrate a digital pH pen roughly every two to four weeks, or immediately if readings start looking off compared to a fresh mix.

What's on the shelf

• Growth Technology — Buffer 4 and Buffer 7 calibration fluid, plus Liquid Silicon for buffering pH swings at the root.
• GHE — Flora Kleen, a reservoir and root-zone cleaner that also helps correct pH drift caused by salt build-up.
• Canna and Ecothrive — pH Down (bloom), Cal-Mag Agent for hard water, and Neutralise for stripping chlorine and chloramine from mains water before it hits the reservoir.

If you're topping up a hydro reservoir daily, water can drift half a point or more overnight as roots take up nutrient unevenly — check first thing each morning rather than trusting yesterday's reading. Pair a meter from meters with your calibration fluid, and see base feeds for the nutrients you're actually correcting pH for.

Express Delivery available, free over £60. Ring the shop on 020 3488 0419 for advice, six days a week.