[mseepman]

I think you would be so much better served by looking at a DIY fixture that you could control all the specs on yourself. I will be building something for myself on the 84" tank I am building that will hopefully blow most prefabs out of the water. Milad is doing another big LED order and the pricing he got on them is really good.

As for your question...I think you will need a larger fixture as you would probably suffer a lot of shading if you go too small. Also, every fixture uses different optics and you'd have to really find the right fixture to do your tank.