The middle-section is actually where I was going to place a cpu fan/heatsink with 3x10w Leds... I'm trying weezards advice of separating the reds and the blues so that I can adjust the height of the two lamps and thereby control the R/B-ratio.

So what you see there is basically the whole thing, except for the aquarium pump and the second lamp of course.

I'm placing the coil beneath the air-intake so I hope that will be a sufficient airflow. If not, I'll try to mount a small fan on it, like you said. As for water-proofing I guess it would be a small catastrophe if there was a leak! I'll make sure to have it running atleast a day before mounting the LEDs to find the weak spots.

Thanks for the replies, much appreciated!

I may have to rethink the independent-lamps plan to utilize the middle section for heatsinking.