I bought a glasscages tank from Poseidon's reef, but it did not have the plastic overflow covers. I had seen threads on RC about forming cultured rock around them or over the back of the tank. Well I measured the overflows and built a plywood form, added eggcrate for a skeleton frame and started mixing cement. Well after mixing a second bucket I should have realized there was a problem. But, at my age thoughts don't always go to the top floor. It was looking good, I envisioned corals embedding in the rock reaching up to the light. I eventually ran out of concrete, figured I would raise the rock off of the bottom of the tank by setting on other rocks. Well today I pulled the forms, and tried to pick up the rock. I did say "tried", it weighs in at 70 lbs. I figured tomorrow I will call glasscages and see about those SWEET plastic overflow covers. Also plan on breaking up the rock for use in my fuse. It takes a big person to share such a embarrassing situation.