news group requested info on Aqua Mats:

Found this place: http://store.premierwatergardens.com/aqst.html Standard
size for $75 and a mini version for $30.

I do remember a discussion about a homemade version using black trash bags.
Seems to me it went something like: silicon a non-bouyant rod inside &
along the side of one seam, then make cuts 1-2" apart down to and just
above the rod. Cut to the height you want it or vary it. ~ jan

~Power to the Porg, Flow On!~