With a 2 bulb fixture, you can use the legs that come with most fixtures that will put it about 3-4 in off the surface. You could also just lay it on top of the glass, if you have a glass top. There are also mounting kits to suspend the lights from the ceiling should you want to go that route. Even if you lay it directly o. The top of the tank, if the fixture has even mediocre reflectors (most t5ho fixtures have individual decent reflectors for each bulb) you will get full coverage. Florescent bulbs, when properly reflected, are the best source for diffused lighting of an entire tank. MH
lighting is great, but you have to be much more mindful of "hot spots" with these types.