Originally Posted by Philsuma
I would make sure that hooded lighting doesn't raise the tank temp too much.
That's a good observation. These pictures don't show the standoffs for the lights I used for this tank (some plastic deli containers :-))
I usually select the standoff distance from the tank based on the lighting. If I suspect it's going to fry a plant or the light distribution isn't quite right, I'll adjust their height (for me, I just choose different size deli containers :-))
This selection process can sometimes take a few days (I'm OCD about it).
The temps in my tanks are a pretty consistent +2.5 to 3F compared to ambient. I've taken periodic measurements for a few years now with different lighting, and I've gotten lucky that the lights I've chosen have been consistent in that arena.
These specific cree bulbs are safe for enclosed fixtures, which most likely explains why they don't turn the tank into an oven when there is at least some airflow between the lights and the tank (and I would be curious to measure tank temps when they are right against the glass). The energy lost as heat has a difficult time transferring to the tank as cooler air flows in the bottom of the fixture and out the top holes.
If someone would like their lights closer to the tank, I would recommend the 60w. I like and use 75w because they can be raised a little higher, and the light spread seems more natural to me.
This was my final choice on light height: