We use Turface or Soil master select widely in the USA.
It runs about 16$ for 20 Kg bag.
Japan is mostly like Hawaii, old volcano so the soil is volcanic......no peat moss, no pine bark, etc. Akadama is literally dug out of old Cryptomeria Forests of Japan at about 10 feet depth. It's piled up on concrete areas to let dry, then it goes through sifters to separate the grain sizes. It is flashed fired to remove any organic matter that may have blown on it or somehow visited it during its "curing" process.
One of my other hobbies is bonsai.
SOIL TYPE CEC
Sand 0.1-5
Akadama 21
Clay 20-50
Organic Soil 50-100
CEC (me./100g) Matrix
- -----------------------------------------------------
<0.1 Clean sand
24.3 Clay Soil
27.0 Kitty Litter
1.7 Fluorite
ADA is about the same as clay.
Flourite is lower than these(other than sand).
See Jamie's article:
http://home.infinet.net/teban/jamie.htm
I use dolomite without issue as a sole sediment in 3 of my aquariums, it's cheaper than SMS, Turface, Akadama etc.
I chose it for aesthetics, not nutrients etc. If I chose a sediment for fertility, I'll go with soil clays. If for cost and aesthetics, well..........then it's less of an issue and I can dose the water column. I guess my question is it really much better than say sand? I see little evidence in terms of CEC and it's pretty nutrient free otherwise.
Without testing it(the soil), it's difficult to say what the results are or are not due to the sediment alone irrespective of things lighting, CO2, and other general care. Plain sand can do a dandy job based on pics and good care as well.
You can do pot test, this works very well with terrestrial plants and should be the same for aquatics(emergent plants are not subjected to CO2 issues or to water sources of ferts, so it's all 100% sediment and nutrients contained there).
Small pots in an aquarium can be used also. CEC and nutrient analysis is already available for this Akadama. Still, cost a bit more than sand and you could add worm castings, osmocoat, soils etc to a base layer.
That would take more demand off the water column, thus making it leaner and still get the same growth rates, and thereby reducing water changes and less RO use.
Lower light will also do a similar effect.
Regards,
Tom Barr
I don't care much for the color and the grain seems rather rough for the kind of fish I keep, but substrates are so subjective. Reminds me a bit of a combination of flourite and laterite, but seems much less messy, flourite was ridiculously messy. Glad you like it, 'cause it really would have bad if you didn't. 
