Sufficient lighting?

[tzhanks]

My tank is 25" deep and i would like to be able to keep a mixed reef, and a clam. I am thinking about going with the 20" nova extreme pro.

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=18700&cmpid=03csegb&ref=3312&subref=AA&ci_src=14110944&ci_sku=0035962000000

Would this be enough light?

[FireWater]

What are the other dimensions of the tank? Will this cover the whole tank front to back?

Short answer is yes that light will work and be sufficient.

Long answer is there are several fixtures and types of lighting that will work. I have the 48" version of that light over my 90G and it is 25" tall