I recommend a combo of MH & T-5 lights. For the 125 you would need 2 250w MH. One for each 2' of tank and the T-5 for actinic's ~2 54w's and you should be good to go. I know that the 125 is 6' but the MH's in the center and that should do it. As far as additives, you should not need anything for the first 6-12 months. Let the tank mature for 4-6 months, add a few corals and go from there.