T5 HO To 250W MH Question

[mantisman51]

I have a new 250 watt 14000K MH fixture being sent to me this week. I should have it by Friday at the latest. I currently have a 48" 216W T5 HO unit with 3 54W 12000K and one 54W blue actynic and a single bulb 50W T12 AllGlass natural daylight bulb-no K rating listed. I have a 125g reef with all my 130# of LR in a 4' long pile in the middle of the tank-from the bottom of the tank to within 6" of the water surface. I intend to keep the T5 unit in the canopy and hang the MH unit about 2' above the water surface-where it will spread the light across about 2/3 of the reef. 1) Will I need to start by just having the MH turned on for short periods of time to allow the coral to adjust to the higher light?(will too much exposure burn the mushrooms,xenias,Kenya tree and bubble coral) 2) Is 2' from the water surface too far or close to the water surface?

 

[natclanwy]

2' is a little too far from the water, most of the light will hit the walls of the aquarium, and a MH will only light an area about 2' square so you will only be lighting 1/3 of your tank.
The halides can burn your corals, I would use black plastic window screen in layers under the halide to shade some of the light and remove a layer every couple of days to acclimate your corals to the new light.