I am also looking into a suitable grow bed media now.. currently i have (the local version of) Hydroton under investigation as well as Perlite, both of which i can get 100L for 50€ which seems to be the cheapest alternative. I currently have a small batch of expanded clay used in construction works but that media floats so that will do me no good in the grow beds, as it will move around and/or overflow the bed.
Anybody have any experience with Perlite?
Also, anybody tried charcoal beds? from what i have found out this evening that might be a viable alternative