Walter I would like to thank you for the article on using "modern" media in growing bonsai and your methods. Also to everyone else who has contributed there own or researched information. All usable by any of us to find our own happy medium in the search for a suitable medium
Personally I have always had atleast one tree in some sort of 100% inorganic media and trialling several at the moment (crushed rock/tile/brick, scoria, blue metal, diatomite, attapulgite, akadama) as well as various combination mixtures. As has already been pointed out the key to succeeding with them is to give adequate food & water, way beyond what you would think needed. I have always been a heavy waterer and am finally working out how much food the trees want & need to really get good growth.
With regards the use of hydroponic fertilisers, it is something I have played around with in the past. I was using a mix of crushed rock, terracotta tile and perlite. The main problem I found was excess salt build up, even with regular flushing of the mix it still seemed to build up very quickly, going from good to not good for the trees in no time. I couldnt solve the issue so gave that experiment up. They could be good for a boost once every now & then but I will stick with organic ferts for now.
Matt