As I stated a long time ago, I have taken an interest in putting together some light weight media for media beds or towers. Hydroton is way too expensive in South Africa, and I was looking for alternatives to have as media that was lighter than gravel. A while back I mused about the possibility of getting some pvc granules and experimenting, and then shoved the concept onto the back burner. As I am now getting ready for spring planting, I'm finishing off some towers and experimenting with media. Coir is not doing it for me, with the water channeling in the tower far to rapidly and creating uneven water flow and dry patches.
So I went back to the pvc granule thinking. I got hold of some virgin pvc used for injection moulding, and here is my first test run. I basically heat them to a point where they become sticky, and then cool them rapidly again, resulting in a "peanut brittle" aggregate. I mix these with vermiculite and use them in te tower to experiment with. They hold moisture much better, and the flow is better too. I do not know how much different the weight of the tower is compared to hydroton, but I like the overall effect of moisture retention and surface area creation that this combination gives. It is a lot cheaper than hydroton too.
I have fitted spray heads to all my towers, and the water delivery is good but without washing any of the vermiculite out again. The tower also stays moist for much longer than what my current flooding cycle is.
Kobus, an update if you will.