x_size = 30; // horizontal outer size of the aquarium pedestal.y_size = 30; //thickness = 10; // thickness of wallsrim_height = 10; // height of upper rim for fixing the aquarium in position.difference () {rotate([0,0,45])cube([x_size, y_size ,thickness]);translate ([0, 0, thickness)cube([x_size - 2* thickness, y_size - 2* thickness, thickness]);cube([x_size - 2* thickness, y_size - 2* thickness, pedestal_height - rim_height - thickness]);}