How do you use Silica in Coco?

You can but always add the silica first and mix well

that was written before i saw any other response.. if it stepped on someone's toes it was a generalized statement only.

Plants need very little silica. Regardless of what AN instructs, i'd do some research for more educated answers than you'd get from the peanut gallery. AN has a habit of being a greedy little punk bitch manufacturer... splitting things into 10+ products when you could mix it into 2 or 3 safely. There's no need for 12 bottles of various fertilizers and supplements.. that's just greedy/predatory business practices. looks like soil typically contains 14-40 ppm out in the wild.. that doesn't mean it is optimal, but will correlate well, i bet. Using vermiculite can add available silica to your substrate, too

I would go with what the company recommended meaning it's been tested and tried, not something random on the internet.