I am currently growing 3 autos in coco coir/30% perlite, 3 gallon pots, and they are at day 18 since sprouting.
The instructions I am following (https://www.growweedeasy.com/coco-coir) say to keep the pH between 5.5 and 6.5. I therefore adjust the nutrient solution (Fox Farms Big Bloom and Grow Big, 1/3 strength, Cal Mag full-strength) to about pH 6.0 before watering. I am using a good pH meter (Apera), I frequently check the calibration with pH 4 and 7 standards, and it has always been spot on.
However, when I recently checked the pH of the runoff after watering, the runoff had a pH of 6.9 (the same for all three plants).
I therefore decided to water some more (since the Coco was already saturated) to try to flush out the high pH liquids, and gave each one another 500 ml of nutrients at pH 5.1. Again, the runoff had a pH of 6.9.
So something in the Coco is raising the pH. I made up the Coco according to the instructions in https://www.growweedeasy.com/coco-coir - I hydrated it in water at pH 6-6.5 with Cal Mag and let it fully drain, but I didn't wash it more extensively. The Coco I used was this one: https://www.amazon.com/dp/B06Y2K5JMB?ref=ppx_yo2ov_dt_b_product_details&th=1
​But it seems that something in the Coco, which doesn't wash out easily, is raising the pH to 6.9, even when it is fed at pH 5.1.
Should I ignore this and just continue feeding it at the right pH - or should I flush the pots with Cal Mag, pH 5.5 or so, until the runoff is a similar pH?
The instructions I am following (https://www.growweedeasy.com/coco-coir) say to keep the pH between 5.5 and 6.5. I therefore adjust the nutrient solution (Fox Farms Big Bloom and Grow Big, 1/3 strength, Cal Mag full-strength) to about pH 6.0 before watering. I am using a good pH meter (Apera), I frequently check the calibration with pH 4 and 7 standards, and it has always been spot on.
However, when I recently checked the pH of the runoff after watering, the runoff had a pH of 6.9 (the same for all three plants).
I therefore decided to water some more (since the Coco was already saturated) to try to flush out the high pH liquids, and gave each one another 500 ml of nutrients at pH 5.1. Again, the runoff had a pH of 6.9.
So something in the Coco is raising the pH. I made up the Coco according to the instructions in https://www.growweedeasy.com/coco-coir - I hydrated it in water at pH 6-6.5 with Cal Mag and let it fully drain, but I didn't wash it more extensively. The Coco I used was this one: https://www.amazon.com/dp/B06Y2K5JMB?ref=ppx_yo2ov_dt_b_product_details&th=1
​But it seems that something in the Coco, which doesn't wash out easily, is raising the pH to 6.9, even when it is fed at pH 5.1.
Should I ignore this and just continue feeding it at the right pH - or should I flush the pots with Cal Mag, pH 5.5 or so, until the runoff is a similar pH?
