[Delphinus]

Two bulbs will certainly give you a better spread..

As to whether 2-175's is better than 1-400 though ... I'm not sure.

I've had clams under 2-175's though, and they did seem to do OK under the lighting. It was issues other than lighting that I don't have those particular clams anymore.

If you have the ballasts anyways, why not go with all three? 2-175's flanking the 400. That'd be an INCREDIBLE setup. You could even consider maybe one of those Radium 20kK 400W's. Oh man ... I get goosebumps thinking about how good that'd look.

:D