Above Fluorescent tubes vary considerably in terms of their spectral output at different wavelengths. With careful experimentation, it is possible to achieve a lighting system that satisfies the needs of the fish and algae, as well as the invertebrates, in the aquarium. Metal Halide and some Mercury vapor lamps produce the very bright light essential for deep invertebrate tanks. They can be very effective when used in conjunction with .03 actinic blue fluorescent tubes, using a reflector over the bulbs directs more of the light to the tank, cooling the lights also helps reduce heating of the tank and lengthen the lights life. You should also shield the lights from direct water splashes and evaporation / condensation to prevent water damage.