w/ that much coco, may be too water retentive to add...
earth worm castings @ 10-15%, total volume...
or, add more perlite, to ~50%, then mix 50/50 ewc+coco...
ewc can become water-logged w/in the media & cannot see unless use cheapo soil moisture meter, or dig fingers in. pockets of soggy media ca, accumulate if too much added. coco already holds nice # of water...
Question: How actively do EWCs buffer PH, and how close to neutral will it push the root zone? I know that humus is an important part of PH stability in organic soil mediums, what's stopping me from tossing some EWC into my coco is that I don't want it to push my PH above 5.8 - 6.0.