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Its made out of polystyrene. I used non toxic acrylic paints and grout to add texture I patted the old brush on the wet grout.
I hope you all like it sorry its not a long post Im using wood adhesive to seal it which is also non toxic i also made a cave in the big rock if you can see it
I carved out the rocks by using my finger nails Hope you like it
EDIT: The vivarium is much bigger than it looks in the picture.