Any long nap internal rug or artificial turf or door mat material would work. One can buy various filter mat materials from places like Aquatic Ecosystems but this would be more expensive than using used carpet or remnants. Contact carpet installers for scrap pieces of carpet. Offer them a few token dollars so they keep you in mind for buying their scraps. Shag carpet would be a good example, but any mats left in the pond a long time without rinsing will likely load up with algae and detritus. Place mats in spawning pond for only a short time before removing to rinse fairly frequently (every 2-4days) to keep the material relatively clean so any laid adhesive eggs will stick to the "fibers". If your timing is right, mats will contain eggs for transfer after 12-24hrs.
