Walter Pall
Masterpiece
Ok, there are lots of great options for soil as has been stated previously. Is "Akadama" a ""Super ingredient"? Probably not. It is good stuff though for a water retentive element with a good particle size.. Yeah, it breaks down over time as roots fill the pot, but according to some this is beneficial... At the very least it seems a good indicator of when is a good time to report the tree!
If I had to point to one ingredient that is seemingly MADE FOR BONSAI (is is NOT, but just seems like it is perfect, may BE the "super ingredient") I would say it is pumice!
Pourous surface- lots of areas to hold water and for water evaporation/ ion exchange.. All that good stuff.
Irregular shapes- when coupled with the fact it does not "break down" into mush, this means it retains a pourous soil structure..
JUST heavy enough that it won't float right out the pot easily like perlite, but light enough that your pot won't wish to more than it should because of the addition of pumice to the mix...
Light color somewhat unappealing, but it is not completely STARK WHITE like perlite..
Overall, I have found that pumice mixed with anything (turface and Pune barked JUST pine bark, Akadama, lava And Akadama, PEAT for peat's sake, COMPOST...) I have tried for bonsai mixes has it been VERY successful, and many of the experts out there use Pumice alone to plant collected material in as a means of bringing it back to health, so I imagine pumice ALONE is a fine bonsai "soil"... Kanuma is after all a type of pumice basically and many people swear by it as the sole ingredient for Azaleas...
So, if affordability, availability... Is an issue, then this may be the best part! Pumice is relatively affordable compared to Akadama and even a bit cheaper than lava in my experience! If you want to "splurge" and get one great ingredient to add to your "budget bonsai" mix, make it pumice. You can find LARGE bags on eBay.. 3 gallons +, For about $23 or so including shipping! Easily worth it IMO...
Amen
Walter Pall