Looks like the led fixture is a thin strip. IS there enough spread to cover your tank's footprint since your light is just sitting above your tank? I have always wondered about that with LED lights.
I was worried about that as well, Nick at buildmyled.com helped me choose the right lens for the LED lights. They are not bare LEDs on the bottom pointed down, they use a lens to get full coverage.
In my case, I wanted a single fixtures so we did a 75 degree lens.
They have everything from 0 to 90 degree dispersion lens. I will put this in my review as well.