I just bought one. I'm using it as the light for my 30L invert/sensitive fish quarantine tank. No corals in there at the moment, so can really only offer impressions. I have it quite high over the tank in order to get full tank length spread. My sense is that it would do a 12" cube just fine with the light 6" above the water. I 'think' it would grow SPS, though perhaps in the top 6" of that cube. It's only a 15 watt light, so perhaps I'd be inclined to go with a 160 for SPS in a display.