What Led fixture to get

[sphelps]

There are too many threads comparing these two fixtures already, plus everybody knows that if it doesn't have at least 8 colors it's not worth talking about anymore

[Nano]

One ai sol covers 24x24x24 inches your could get away with that no problem I have one on a 24"cube no problems with coverage. I like radions for the color spectrums but for what your paying for it it would be a waste for a tank that size, as more then likely you wouldn't even use it at half power. I only run my ai sol at 35% and my corals are doing really well under it. Might even think of holding out til the ai Vega comes out, it has many of the same color spectrums as the radion but still a fraction of the cost

[Lampshade]

Check out:
http://www.manhattanreefs.com/lighting
In the LED section he has par values over area coverage. LED PAR values are a mess right now while people argue about "good PAR" vs. "bad PAR" but gives you a good idea of the coverage of the fixtures

Overall it comes down to what you want to spend. You can make anything work from a used 250W halide for $100 to a $800 radion fixture.