How much light

[Splendid Warrior]

Hello, can anybody tell me would 2 x 250w 10k MH and 4 x 18w flourescent atinic lamps be sufficient for a 120g tank measuring 5L x 2H x 1.6D? I intend to keep sps and clams. Thanks for the help. :)

[DJ88©]

With an 18" deep tank you should be ok. Just make sure that you are keeping the high light requiring critters under the MH as much as possible. :)

[flyfisha1]

I recently built a 110-custom tank for the living room; originally had intended to put 3x250-watt MH and a pair of 65-watt PC actinics. The MHs were to be a pair of 6.5K and a single 14K (Venture), but the 6.5's were too "yellow", so ran the 14K with the PCs alone for three months and got pretty good results (several clams, assorted LPS, soft corals, polyps, mushrooms, sponges, etc.). Switched out the 6.5K bulbs for 10K Bluelines (also reportedly 14K), pretty uniform blue-white appearance. This morning, switched the single 14K out for a 6.5K, man what a difference! I'd say that the actual intensity of the 6.5K bulbs is much higher than that of the 14K bulbs, and the overall appearance of the tank is more pleasing now, since warm colors are a little more bold and less washed out. I'd guess that the CRI of the tank just got a lot closer to 100. So now the MH mix is a pair of "10K" and one 6.5K, in addition to the PCs. All are run on PFO ballasts.
This tank, BTW, is 36"x24"x30". This may seem like a lot of light to some, but I've been doing this for many, many years and haven't had any trouble with intensity of this kind. No chiller to keep heat down, just a 15" fan blowing across the lights and the water temp never gets over 79. This is with a pair of MD24s running the game.