I have discovered a new soil component that I feel to be superior to Akadama, and I thought everyone might like to give it a shot. It has a very similar composition, proper grain size, sharp edges to encourage finer root growth, and is noticeably less expensive.
It's called Flourite. It is made by a company called
Seachem and is intended to be used as a substrate in planted aquaria. It has a high iron content and is very porous. It seems to hold water well while remaining free-draining.
I have used a mixture of Flourite and Potting soil (1:1) in my houseplants and outdoor container plants for years with great success, and have just recently begun using it as a bonsai soil. I have potted two japanese maples in training pots with only Flourite as the soil and they seem to be doing well. The very top layer dries out within a few minutes, but just a few grains down it stays moist for literally days. Granted, these are in deep pots, but I think it might be worth a shot in shallow bonsai pots.
Oh, BTW, I work for the company, so my motives aren't
entirely selfless, but I do think this is an outstanding substitute for Akadama.
And no, I can't get you samples. I had to buy mine just like everybody else. How's that for gratitude, huh?