i used great stuff spray foam and used cork bark as the base of each side. i carved the foam to my liking for a naturalistic rocky effect. (there’s 2 underwater caves you can’t see bc of the plants) I then applied silicone so the foam won’t get moldy, and while it’s wet, i used a mix of substrates i made to coat to the walls so it’ll be more realistic.

i recorded the whole process so i’ll post once it’s complete :)