Originally Posted by
SantaMonica
Welcome from Australia.
Although most China lights only actually have about 2/3 of the wattage they state, the 120w one is still way to much. You don't say how much you feed, but probably 3 to 5 cubes a day based on 22 reef fish. So although you could do a smaller screen than 10 x 12, if you use the lights you found, they would shine around (and miss) some of the screen. So 10 x 12 is fine.
The 30w one with multi LEDs works well; one on each side, about 5 inches away.
And the 30w version of the water resistant one works well; one on each side. 50w is too much, especially two of them on each side. You might have been thinking of CFL lights instead. LEDs only need half (or less) of the wattages for CFL or T5.