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Just guessing at how deep your 240 gallon tank is I would have to say those bulb would not penetrate very far. What do you plan to keep in the tank? If it is to keep corals or clams then you will need MH lighting or at best compact fluorescent. Look at the options on http://www.hellolights.com
Please post the dimentions of the tank but if its deeper than 24" I would go with 400W MH's every two feet and then use PC or VHO for actinic supplementation of the light. Now the above suggestion is if your going to do a reef. If your doing a fish only tank then yes the lights you have would give you enough light to see the fish.
Is it OK to run only 2 400watt MH and have my rock pilled on the sides with the middle as a valley. The bulbs are 10K k would it be OK to run 4 36" NO, actinics for the timebeing until I can afford VHO or PC or will it effect my rock growth and anemonies