Soltan, a guy in our bonsai club sells it. It is sold primarily to orchid growers. I only use the fine mix, the others are too bulky. The fine mix works instead of peat, to keep the mames and some of the tropicals happy. I pay him about $15 for a bag, which lasts a long time. Kuma Bonsai Nursery also carries it. (
www.kumabonsai.com)
The nicest thing about the coir is that it doesn't resist water when dry, as peat does. You can rewet the coir easily. It retains water and still allows air to pass through. It doesn't seem to break down, but since the mame get repotted at least once a year it wouldn't really matter if it did.
The component that I am most interested in, and pleased by, is the coir. Not the diatomite. Although the diatomite seems to be the biggest selling point for them, it's hard to see that it brings that much value to the tiny trees. Their claims that diatomite makes silica available doesn't make a lot of sense to me... do plants need silica?* And some of the claims... "lateral movement of water and nutrients"... well, duh. Most substrates would allow lateral movement, wouldn't they? Unless you were using stalagmites or something. Read
here for a list of attributes of diatomite. The water retention, however, is useful.
Lindsay Farr has mentioned using the diatomite on this forum, you might want to contact him for an Australian supplier.
*if plants need silica from their soil components, are we supplying silica when using perlite or scoria or turface? Wouldn't the silica being made available, mean that the actual components of the substrate were breaking down? Does someone have more knowledge of this?
Joanie