shimmering only works if you use metal halides. I don't know how much money you want to spend on electricity especially if you are running a fish only tank.
If you decide to go with halides, think about Lumenarcs. They have good reflection rate and cover a huge area. Look for sanjay's website on light comparison and it should be under articles for the review.
I have a 8' x 2' x 2.5' or 3' (l x w x h). Two lumenarcs position correctly lights up the whole tank minus a couple inch from each side. Three would've light up the tank with ease.
If halides aren't your cup of tea, you can go with cheap t5 or home depot workshop lights (i think thats what it is called). Its cheap and effective. Theres a site with mix reviews that sell cheap t5s.