Extra Thick Japanese Filter Mat Aquarium Koi Pond Media Pad Custom Fit Sizes (20" x20" x1.75", Japan Mat)

Probably one of the best investments I've made for my pond. This stuff is durable, thick.. it's amazing.. I recommend it highly, .. Keep in mind it's made to last, and is tough to manipulate and cut, but is possible. I just kept it as the size it is... It traps the muck muck quite well

Too porous