Stargate Style Tower for Fish Tanks

Help with my next creation!
Again I felt like my fish needed somewhere cool to hang out so I quickly throw this together. intended to fit into the corner of a square fish-tank and give them somewhere to chill. The writing on the side reads "our fish are spoilt" The little slot at the back to to put a rock in to weigh it down. Personally I am putting a 10mm brim on it and I will just use that with gravel to cover it over.