Does this substrate mix work? What could I do to improve it?

2 Parts Sphagnum moss

1 Part Coco fiber

1/4 Part pine bark

Also, can I add a bit of potting soil? I know people don’t recommend it due to the fertilizers potentially harming the microfauna. However, I‘ve been keeping my microfauna in potting soil (I didn’t know it was bad) and they‘re doing fine.