I am pretty sure Peepaw makes plastic habitat from bottles to sell. Grinds them up and places them in plastic netted bags..or something like that. One link I could find is below.

http://forums.pondboss.com/ubbthreads.ph...amp;Search=true


Here it is:
http://www.fishiding.com/artificial-fish-habitat-fish-feeder-bag/

possibly you could simulate the idea the best way you can.
Most important, Have fun!!!!!