Just remember, a set of sieves is your bonsai friend. Any media can be improved by using sieves to make the particle size more uniform. Eliminate fines, eliminate big chunks. Life will be better. I sieve components before combining, and then do a "quick shake" sieving again after the blend has been mixed. Sometimes the act of mixing creates more fines, so the final use of the sieves is important.
Finer mix for small pots. A more coarse average particle size for larger pots.
Napa 8822 Diatomaceous Earth is very fine, really only suitable for the small pots less than 4 inches or so in diameter and 1 inch in depth. It pairs well with a brand of pumice named Dry Stall, the two products are nearly exactly the same size range. This blend is really very fine particle, too small for most purposes. If you sift carefully it will drain well even in medium size pots, but generally it is too fine for anything larger than small shohin bonsai. Turface MVP is also about the same particle size. Again, too fine for my tastes, but useful for very small pots;.
I prefer a more coarse brand of pumice that I get through Ron F of the Milwaukee Bonsai Society, also known as Ancient Arts Bonsai. This is more in the 1/4 to 3/8 inch particle size range for small and medium size pots. It pairs well with "seedling grade orchid bark" a small particle douglas fir bark sold around the orchid hobby. Ron F also has a source of a more coarse DE, I forget the trade name for it. This grade of pumice matches well with small and or medium Akadama and Kanuma.
Hit your local Marijuana Grow Supply Shops for pumice and perlite in various sizes. They also may have DE, diatomaceous earth, and various fired or calcined clay substrates such as Turface, or Haydite in various particle sizes. Also check out your local Farm Feed Stores. I have found interesting substrate possibilities at Rural King, and Blaine's Farm & Fleet. An old school substrate is crushed granite or crushed quartzite, sold as grit for poultry. Turkey grit is the perfect size grit for medium bonsai, particles average 1/4 inch give or take. Cherry Stone brand out of New Ulm MN, has a beautiful purple brown colored quartzite grit that is a gorgeous top dressing for bonsai. A little green moss, a little cherry stone, and the look is lovely.
Pigeon grit is a nice small particle grit, but usually has anise and other herbs in it as attractants to get the pigeons to forage through the grits.
Grower grit is fairly fine particle for young poultry, Layer is more coarse, Turkey grit is around 1/4 to 3/8 inch particle size, and if your Feed Store is in Horse Country, where the "Ordinary People" live, Ostrich grit is roughly golf ball size particles of granite or quartzite. Yes, the feed store near me has grit for Ostrich and for Emu. I'm in town where the common folk and servants live, but a few miles out into the countyside we have "horse country" the Temple Lippizan farms, and a couple farms with Friesian, Percheron and Clydesdale horses that they use to keep their Arabian and Thoroughbred horses company. These people keep enough emus, ostrich, peafowl and other such stuff that a trip to the Wadsworth Feed Store is a bewildering selection of items for exotic breeds of birds and livestock.
Grower grit and Turkey grit are the two sizes that seem the most appropriate for bonsai potting media where, or if, or when you choose to add an inert component to your mix. Granite and quartzite grit holds less water than lava, and much less water than pumice or perlite. The three benefits of granite or quartzite grit are #1 - WEIGHT and #2 LONG LIVED STRUCTURE #3 - holds almost ZERO WATER
In shallow pots, the weight of the grit will help hold a tree in place, though nothing beats a skillfully wired in root system. Really, learn to wire your trees into your pots, then the weight of the media won't matter.
Long lived structure - granite and quartzite will NOT break down, even after a millennium of freeze thaw cycling the grains will be largely intact. If paired with other long lived media, you can create a mix for that tree you don't want to repot for a decade at a time. Junipers like their roots to be left alone, a pumice-quartzite-lava mix with maybe just a little Akadama is perfect. You will only have to repot when the tree needs repositioning, not because the media has broken down.
Crushed granite and quartzite is perfect for drying out a mix. If you have your watering set up automated for twice a day, you might want to use a mix that does not retain water. If you are using clay products like Akadama or Kanuma, which hold a good deal of water, you might want to dry out your mix some by adding some crushed stone. Crushed lava is used for the exact same purpose.
So crushed stone is an "old school" media. it really is only good if you are careful to use your sieves to get particle sizes uniform for your mix. If you have a poorly graded mix, with a wide range of particle sizes the weight of the crushed stone will help form compacted layers in your pots and really mess you up. A really horrible mix is grit mixed with a fluffy peat moss based packaged potting mix for African Violets. You will have hard, compacted bricks of peat and stone in no time at all.
Fluffy peat moss is bad, bad bad. Trust me.
But if you can find the "chunky peat" that stuff is good. But I will save "chunky peat" for another post, another time.