I don't have any experience but I've been meaning to get some to try. The company name is Hydroton, or at least one company that makes it... They are a hydroponics medium that offers a different option and technique for growing plants.

Hi
I've used the stuff but switched to crushed lava rock. Has all the same properties and costs about a third of hydroton or leca. gary

How do you know when it's time to water? Is it different from bark medium? I'm not sure I want to switch now that my orchids are performing well. It does seem to act as a better "anchor" for big orchids.

Andrea, as has been tangentially mentioned but not explained, the medium you are talking about is called LECA (light expanded clay aggregate). In a mix, it functions just like charcoal and perlite: it is inorganic so does not break down, and increases drainage within a mix (opens it up).

As a solo medium, it is great for plants that really need to dry out fast (i.e. Vandas/ascocentrum, etc), plants that need to be mounted or in baskets. Its not easy at all to overwater a plant in this potting medium in most cases. Its also the primary potting medium used in Semi-hydro (google semi-hydroponics and check out the first link for a full explanation) that a lot of us use to grow our plants.

You will find that you will have to water much more often. LECA does not hold much water, hence the propriety for dry loving plants. As Gary noted, lava rock is also available to accomplish the same thing. Dracaenas obtained from Hawaii are often produced growing in lava rock. It is definitely cheaper than your LECA.

When I started growing Orchids the potting medium was osmunda,how things have changed.

Terpguy hit it right on the nose.

In fact I found out in my case that most of teh orchids I tried in using this stuff didn't stay moist long enough and I was loosing many to being too dry. I had to water every day.

The orchids he mentioned love this stuff and those I have left alone.
Of course teh conditions we subject the to makes all the difference too.

Thanks, Meyermike. I don't like this orchid being in Hydroton because if it's a brassia or a related variety, it's not going to stay moist enough. I'll repot it after it's finished blossoming. My feeling about media is, if it's not broke, don't fix it.