Hi Matt,
I found the following at this website which I was directed
to by the fine folks in this newsgroup:

http://www.wavepumps.com/state_of_the_art_filters.htm

"Hollow Media
A newer development is hollow media. If you took a miniature plastic "hollow
drinking straw", and formed internal walls inside it, you would not only
have the external surface area, but also an internal surface area. They are
5 mm in diameter and vary in length from ¼" to ½".

This media has 750 square feet of surface area per cubic foot. So a filter
with 2 cubic feet of media will have 1,500 square feet of surface area, and
will be able to process 150 grams or 1/3 pound of food per day. This is over
4 times more efficient than bead filters, but 1/10th of the sand filter's
surface area.

Its cost when used in a filter is about $0.75 per square foot of surface
area or more than 3x sand.

The first disadvantage of this new media is the difficulty of manufacturing
it. The units are obviously very small and have a very complicated design,
which makes them very expensive at about $200/ cu ft.

The second disadvantage is they are made of styrene. You can test this by
putting some media in water. If it sinks it is most likely styrene. Another
test is to burn it since styrene burns with a black sooty smoke. Styrene
oxide as a contaminant of styrene is known to be very toxic to bacteria,
which would be a disaster to bacterial colonies for nitrification."


Hope this is helpful,
Mark