I have made a small unit using 12 Cree XT-E cool white, for my nano tank.
Basically its the same as the one by Korakot in this thread http://ukaps.org/forum/threads/diy-led-lighting-help.27152/
I have not used fans on mine as the space in my hood is a bit limited but it doesn't appear to get hot at all.
Will probably add fans to it when I upgrade the tank and possibly add a few more leds.
thanks m8 was it easy to put together ?