I have a canopy, took off the lid. Opened a 4 inch hold on each side of the canopy for fans one blowing in and one blowing out. Then I put 2 small aluminum square rods across the top so the light fixture sits right on top and I made it so the bottom of the light fixture sits flush with the top of the canopy.
I had 650 watts of halides on my 100 gallon display with the two 4 inch fans blowing and never ran a chiller. Not saying to do the same but it worked for me. Never got over 81