Fan placement
 

Had to hook up a 6in fan to keep the tank temp down(35.4' C :eek: )
The back of the canopy is open so I secured it to the back,blowing air towards the front.Should I put in on one of the ends of the canopy for best results?The temp has dropped to 28C in a couple of hours.
I'm running a 250w 10k mh and a normal actinic bulb over my 54gal.

I would expect that if air is moved across a larger area of your tank, then it would help a bit more in terms of cooling your tank. So in this case, then yes, I think mounting the fan on one end of your canopy blowing across the surface of your tank would be more effective. Just keep in mind that using a fan as a means of cooling your tank will lead to an increase in evaporation. I'm not sure if two fans are needed for your tank, experiment with one first.

-Richer