[Stones]

I did a similar LED retrofit on a 34 gallon red sea max. I used 20 x 3 watt bridgelux leds on channel 1, 12 x 3 watt bridgelux royal blue and 8 x 3 watt bridgelux blue leds on channel 2 and 4 x 3 watt green, 4 x 3 watt red, and 4 x 3 watt UV leds on channel 3. All LEDs are only being driven at 700 mA (but are dimmable) as that is the max output current of the meanwellen drivers I purchased. So in total, I used 52 leds over at 34 gallon tank.

If you are going with Cree LEDs and meanwell drivers, you should be able to get away with ~ half of the LEDs that I used so 25 would probably do the trick so long as you are driving them at close to their max current rating. You might get a more profound disco effect that way however as less leds will give you a greater distance between diodes and fewer point sources for the light to diffract when entering the water.