Today I am going to build a 3d diy aquarium background/backdrop carved from styrofoam insulation and paint. A cool diy craft for any aquarium, terrarium or fish enthusiast. This cost about $30 cad to build. The background does not go in the fish tank, it is placed directly behind but will give the appearance that it is in the tank. The materials used are not fish safe so do not place directly in the water.