Lighting placement question

[tbrew85]

I am mounting 4 96 watt PC retrofits in a canopy over a 75 gallon tank. How high above the water should these be mounted? :help:

 

[reefkprz]

about 5 inches if they have a lens, more if they are bare bulb

 

[tbrew85]

Originally Posted by reefkprZ
about 5 inches if they have a lens, more if they are bare bulb
There is no lens on the fixture but the tank does have glass covers. would you count that as a lens?