Conduit benders have a fixed bend radius. Since you want two bends in the space between the back of the tank and the middle of the tank, you need that bend radius to be 1/4 of the front to back dimension of the tank. I doubt that can be done unless your tank is at least 18 inches front to back. A good alternative is to use two bent conduits, with just one bend per conduit, with the end of the conduits pointing out away from the back of the tank. That requires that the bend radius be less than 1/2 the tank front to back dimension, a much easier thing to do. That's how I have mine made.