Just Metal Halides

[Aquattro]

Greg, I wouldn't mix the two colors personally, but that's just my opinion. If you just used 10k bulb(s), you don't NEED actinics...depends on what you like to look at.
With that tank, you could use a single bulb and have the lower light animals towards the edges. You could use a 400w Radium and not have actinics, but you might need to raise the bulb higher. I probably would only use a singel bulb anless you were going to pack the tank with SPS.