pedestal_height = 130; // height of pedestal
x_size = 250; // horizontal outer size of the aquarium pedestal.
y_size = 300; //
thickness = 10; // thickness of walls
rim_height = 10; // height of upper rim for fixing the aquarium in position.
difference () {
cube([x_size, y_size ,pedestal_height]);
translate ([thickness, thickness, pedestal_height - rim_height)
cube([x_size - 2* thickness, y_size - 2* thickness, thickness]);
cube([x_size - 2* thickness, y_size - 2* thickness, pedestal_height - rim_height - thickness]);
}