First Thanks Speckled One for OP! It inspired me to make my own foam wall. Some stuff I thought I'd share about my build. I pushed the foam flat after 30 min. cure time because I wanted to reduce the size and buoyancy of the foam. Found that after 24 hours cure the foam expanded through the backside and I had to hacksaw the thick areas down. Pic 1. I also found the thick areas had some gooey, sitcky, messy uncured foam inside them! Still on fingers 48 hours later! That foam is evil! The other thing I didn't like twas the "poo" like surface of the foam after it cured so I scored it with a Phillips head screwdriver. Pic 2 As I was scoring the surface I thought maybe I can push a hole through wall to help the curing in any thick areas of foam. While I was at it I thought again why not push holes through the entire wall to increase that surface area of the wall. I plan to have a 3/4" between wall and aquarium and to circulate water back there as well. Pic 3 shows main wall section pre-scoring hole poking!