Thanks for the info.I guess I will go with "if it aint broke,don't fix it".at this time. I am having a hard time keeping my coleus & other "mother" plants from filling my space.
The local greenhouse I go to has a good hydroponic supply. I will check for expanded shale.
sNs

>> The local greenhouse I go to has a good hydroponic supply

It sounds to me like a perfect medium for hydroponics.

It is also used for running tracks and athletic fields. It would give good traction, even wet, and absorb quite a lot of water. And it's cheaper to ship around than gravel, because it is so light.

I have a Metro-Mix formula (although it is a "custom blend" from one of the greenhouse nurseries) that has expanded shale. I like it for potting seedlings up into a larger container, but not for seed starting.