[John]

When we talk about the ability of a medium to hold oxygen aren't we talking about the air gaps between the particles that makes up the medium. If this is the case then it seems to me that plain gravel would be just as efficient as clay gro-rocks.

Or are you guys referring to the porosity of the medium?
I'm using pea gravel and everything seems to be fine, although I was hoping for a faster growth rate vs. soil. It's only been 4
weeks now and I started almost everything form seed so maybe I'm over reacting.

In your experience is there a point in a plants growth cycle when it really kicks in and starts to take off. If so when?

Maybe I need to try gro-rocks and do some comparison studies vs. gravel.