Lighting upgrade

[Twistedpro]

Hi, i have a 21" cube tank with a 150w halide over it with a 12.5k bulb its around 8" from the surface with a 10hr lighting period, i have just bought a 250w 14k halide with 2x18w actincs, what is the best way to swap this over to stop my SPS from bleaching or stripping. I dont have any glass panels to put over the tank

Thanks for any help you can provide