Metal Halide grow lamps should be used for the vegetative stage of growth of plants in your garden in hydroponics. If your plants are ready to start flowering you need to switch from metal halide grow lights for your high pressure sodium grow lights in the indoor hydroponic garden.
Condition of your plants to the more intense light in your indoor hydroponic garden by gradually reducing the distance between the plants and bulbs. An indoor hydroponics garden will be a source of great joy and wonder if once you have it started and the fastest way to clone or clones.