I recently bought some akadama for spring repotting (Akadama (Heat Treated, Super Hard, Medium Large)) only to find that it can be crushed between my index and thumb. I assume that this is a mark of poor quality, but thought I would ask, just to be sure. Once wet, it is even easier to smash. Thoughts?
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Is this the first akadama you’ve used? All akadama crumbles with enough force. How much dust was in the bag?
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Like @nmhansen mentioned the dust in the bag. The amount of dust is the tell tale sign of quality akadama. 
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Thanks for the replies here! For the past few years I have used triple redline, but I never really paid much attention to the dust in the bag. So, unfortunately, I don’t really have a basis for comparison. I dropped two more images below, but I am guessing it will be hard to tell from these photos. I always rinse my mixes before repotting, so I do expect some dust.
The chrushability appears low normal…
What concerns me is the size. 1"+. …? Thats pretty large . I screan out the >1/2" and larger… and use it for bottom drainage layer mix only. Even my largest (3+ foot tall) trees dont get 1" soil mix…
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Just saying…
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I do not think you should rinse your akadama, sifting is sufficient. You will have to let the akadama fully dry out before using. It will become useless mush when you chop stick the substrate and lead to future problems with the root system. 
When you give the potted up tree its first watering, keep watering until the draining water runs clear
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Thanks for the feedback here. I think it makes total sense to use this as a drainage layer. So even with the crushability it sounds like the akadama might be alright.
Great point! I’ll stick to just sifting. Rinsing sounds like a bad idea.
One more question. Has anyone used biochar? Michael Hagedorn mentions it as a possible beneficial substrate in Bonsai Heresy. One of just a few supplements he thinks has promise.
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I see ‘biochar’ as a organic (ie-fertilizer) component. I tried it years ago. Amazingly (imagine that), it dissapeared after several years … I did NOT get a chance to check out the heavy metals content, which could be a concern… It would change drasticly with different sources… and, with the pH of your water leaching ability…
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I do not use it currently.
Akadama, lava, pumice. Sizing for the tree species and environment. Very friable soil mix. Solid Organic fertilizer for the digestible NPK from the symbiotic fungi and bacterial community… (Liquid organic supplements, too.)
Seems to be working for me…
I am not afraid of trying different components. Try them on healthy unimportant trees first… Change ONE thing at a time…I am not willing to kill my best trees, again…
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Bonsai On!
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