Re: Dupla/vermiculite

Vermiculite will NOT increase your cation exchange capacity. Vermiculite 
is not a clay, has low surface to volume ratio and is an extremely poor 
choice for increasing the fertility of your substrate. The only reason 
you might want to use it is to decrease the density of your substrate. 
You are paying top dollar for the Dupla product, and while I feel that 
its not worth the money, there is a lot of experience backing this 
product so IMHO follow their instructions!