I use this fixture on my 30" tank and it working fine for 6 months now.
http://fishneedit.com/new-light.html
http://fishneedit.com/new-light.html
I have this fixture as well. It is GREAT for low / low/med light. It does have some dark spots in the very top of the tank, but it does a pretty darn good job and it is not that expensive.Coralife 30" or 24" fixtures. I got a 30" from bigal'sonline.com a while back and I believe it was about $60 and comes with two 18 watt bulbs. How many wpg are you aiming for and what are you looking to spend?