LED to Replace Metal Halide

As someone who uses the matrix leds for all my DIY lighting I will say they do work pretty well, I use the 10w's rather than the 20w's because they're at the peak efficiency envelope for emitters (9x1w in 3 x series 3 x parallel at 1000ma total to 333ma per emitter) lower current = higher efficiency, which is also why the led companies give you their lumens per watt rating based on around 200-350ma, even cree does this since thats the only place they actually hit their lumens per watt claims, higher current = higher resistance = diminishing returns as you go higher.

120 degrees is no optics, also the shimmer is from any single point light source, it has very little to do with optics, no matter how much a led focuses out over the surface of the water if it was coming from one spot there will be shimmer, the reason fluorescent doesn't is because the light source it's self is spread out so far over the surface so you have blended refraction to the point you don't really see it anymore. A 120 degree output led has a spread that looks pretty much like a halide in my experience.

Heres a little quick video of my 12g with 10w matrix leds over it (previously had been running another tank for a year with 10w matrix leds as well):

Not exactly telling you which way to go just expounding for the sake of informing, brand isn't as big of deal as people might think, the most important part is having spectra peaks where you need them, and thats not hard to pin down where leds peak, the vast majority of white leds (cool white, neutral white, etc) will always tend to peak around the 450-455nm range and have about the same curve regardless of brand, and royal blues can generally be ordered in 445nm-447nm, 450nm-453nm, 453-455nm, 455-457nm, 457nm-460nm, 460-470nm and other ranges easily.