With the 60g on the stand, leveled and positioned near the wall - I left a small gap behind the tank to avoid salt-creep damage to the sheetrock - I needed to determine where to hang the Radion LED fixture over the tank. Using a 4' level, I placed it across the tank and set the light fixture on top. This permitted measuring the fixture from all four sides to get it centered. Hence, I was able to ascertain the distance from the rear wall and the right wall precisely for the hanging kit. ...