Since it's just clay mined from a general region, Akadama seems extremely (emphasis on the extremely) hit or miss. I've got a tank that's been buffering for about 23 months without issue and one that stopped buffering after less than two months. Same water: RO water with GH5.
I'd definitely never use it for anything other than aesthetic purposes. Stories like Liam's illustrate why it's a huge risk to take.