Jacky wrote:
>In Japan activated carbon (from oil palm nut shell, rice, wood
>chips, coconut) is often used in water treatment too for horizontal
>systems with plants. ........

One source of this filter material is softdrink factories worldwide. They
usually have to pay for the disposal of their carbon and they change it
regularly at about 30% capacity. Worth a try in consumer societies anyway,
and you may get paid to cart it away.

Regards
John Harris
Dalwallinu, Australia