Substrate screen mash

[Louis Charles Bruckner]

Agreed.
I have used fine window screen from a local hardware store, just make sure it is made from fiberglass (better because it doesn't rot or get brittle over time like plastic or vinyl)

I also like screen material because I can cut it to form and stitch together pieces to make it form fitting to odd shapes in false bottom vivairums.
I.E around potted plants or water features.