30' Tanks

I have one 175w MH with two 75 watt VHO with clams, in my 29 gallon tank. I am sure I could use a 250 as well and not have any negative side-effects.
I think Qmonroe is talking about 30 inches high from top to bottom rather than a 30 gallon tank.
250 Watt halides should be fine, 250W HQI would be great.

But in that tall of a tank, I wouldn't try Crocea's or Maxima's on the sandbed. Instead put them in/on your rockwork so they get more intense lighting.