I believe The stuff you have is similar to 'Jap Mat'. I use it in my Eheim canister filter for my aquarium.

Aside from collecting gunk, it also is a breeding ground for beneficial bacteria.

To clean, simply shake it around in pond water..tap water contains chlorine which kills the good bacteria.

You can try a well stocked aquarium out let...they should have the material. (maybe call around)

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CHILCUTT~
The secret to a long life. Is knowing when it is time to leave.