Thanks to you all for the nice comments.
I really like these rays, the Niger cats are very greedy as you can imagine but the real contest is peacock bass - i have to throw in a lot of food, 1 Kilo + of fish and this way i can ensure they bass will all fill their mouths and some will sink to the bottom for the rays and cats.
I have LEDs, 4 x 48" units, they have blue in them though, i think they have a white light, a light blue and a dark blue, you get a remote to control how much brightness each colour displays - you can do the whole sunrise sunset thing.
It's very expensive and i have to be honest the quality of light isn't anything better than what a good T5 unit can give.
I've yet to find a light unit which gives excellent coverage and has fully impressed me, i've got to find something for a few new tanks i'm getting so if anyone has any suggestions it would be good to hear them...