I've run the LEDs at full power just to check how hot the fixture got. I'd like to avoid using fans if I can. Fans would mean I need another power supply and small fans make a lot of noise because they need to run at high RPM to move any air.
I'd rather add some heat sinks to the fixture or try a water cooling setup instead of fans. I contemplated doing water cooling from the start. I was going to use a small powerhead and some tubing and pump tank water through the fixture. It could still be done pretty easily, but I need to find some aquarium-safe tubing that transfers heat well.
I also thought about using thermal epoxy instead of screws to fasten my LEDs to the frame and running water directly through the aluminum frame. Apparently aluminum can be toxic in an aquarium, so I scratched that idea too.
Right now I've got the LEDs running at 1/3-1/2 power. I don't have CO2
or ferts yet and I've got green spot algae all over the glass, so I had to turn them down further. Once I've got all the gear I need, I'd like to crank the LEDs all the way up and see what happens. I think a high-light jungle tank running on ~30W of light would a pretty good accomplishment.