It's the stuff that looks like this:

(Not my picture.)
And you're supposed to use it to make these ugly things:

(Not my picture.)
But instead, you can use it to make cheap and sturdy tank dividers (directions here: http://www.ultimatebettas.com/index.php ... 10124&st=0):

(Yes, that's my tank; please excuse the water spots.)
Or cover large holes in the back of tank hoods:

(Also my tank.)
Or a cave for your fish to hide in, or a breeder box net, by "sewing" the edges of separate pieces together with fishing line.
It's absurdly cheap stuff (a couple dollars for several large sheets), and so multipurpose. (And a tank divider that actually works is so much better than a Kleenex box with reindeer.)



