A support arrangement is combined with a reflector sheet and fluorescent light tube to hold the reflector sheet above the tube in a curved trough shape maximum concentration of light at a desired distance from the light tube by varying the curvature in which the reflector sheet is held. An annular piece is detachable to form a larger opening to be fit to a larger tube, while an auxiliary strip can be mounted across the opening to create an opening for a smaller sized opening. The reflector sheet can be held in a reverse bent along its center to avoid light by the tube itself. Two clips can be mounted together at an adjustable distance from each other to allow mounting of a double sized reflector sheet over two side by side light tubes.