Several websites give about the same mix of akadama, etc., and they all say to sieve the particles. Sieves all come in three sizes, so I can get three sizes of particles, and dust.
Given a pile of small, medium, and large akadama, same of lava rocks, and same of pumice (or whatever) how would you choose from the piles for a particular tree? I would guess shohin and mame get the smallest particle, and so forth. Would that be right?

The smaller the particle size, the more moisture it holds. So if you want more air in the mix, you take larger particles.

I keep the 2 largest sizes for newly collected trees, trees with weak roots and plants that I am growing out.

Thanks, Leatherback.

A related question, do you sift out sphagnum moss, too? When I tried that, out of four cups I got a teaspoon or two of medium, about half fine dust, and close to half big chunks and twigs. I don't think I want to throw away 90% of the bag, do I? I do want to toss the twigs.

I do not use spaghnum in my substrate. (Nor akadama for that matter)

Ivan Mann wrote: A related question, do you sift out sphagnum moss, too? .

I use it to keep the upper surface of the soil moist. I cut it with the shears in small pieces, don't sift it and take it out after summer.