u/Floedekage

I'm trying to make a completely closed vivarium, but there's an area where I'd like to keep plants from growing around/towards. Is there something that I could do/make/use to keep plants from wanting to grow?

I was considering doing some tests maybe using copper strips or maybe something "poisinoius" like toothpaste, althoug that'd properly won't last long in a wet enviroment.

Anybody got any ideas or experience with something like this?