Suggestions on how to simulate a cave look with egg crate structures?

Hi, I’m trying to figure out the best way to make these egg crate supports I created for my paludarium look like caves. I figure the best way to do it is to foam them up and then silicon/glue small bits of seiryu stone and dust to the sides and top. Just wondering if anyone has any better suggestions? Sorry for the shitty drawing on the photo lol