花寶隻紅蘭珠, 係呢度出品 http://www.hydroton.de/EasyGreen/engl/e_Hydroton.htm
HYDROTON® pellets are light in weight, do not compact and are completely reusable - they can be cleaned and sterilised after use. They are also inert, pH neutral and do not contain any nutrients. The pellets drain freely and do not hold any excessive water, which is why they provide good oxygen levels around the root and why they are particularly suitable for flood and drain systems. They are also used extensively for rose growing.