Anybody use the PowerBrite LED's for shimmer?

As far as the brightness goes the LEDs don't really add much more because they are more direct or concentrated as the pic here will show (forgive the blur). Pic is of two strips of White and Blue bulbs. I don't know about the coral growth part of your question. Perhaps if you added enough (what ever that would be) yes they may work.

 

I have a couple on my 12G nano, it does ok, but I'm not thrilled with them. I have the white and blue ones, so it gives a very odd lighting effect in the tank since they alternate with white/blue/white/wblue scheme.

 

I have 12 blue led's built into my fixture for moon lights... they are AWWWESOME. Probably my favorite way to view my tank

There are 6 sets of 2... right next to each other in the middle of the fixture.