Thanks for ideas. Yes I think I need a more powerful fan to suck air in/out of the hood. The back of the hood is open always (front optional), but I noticed last night I can only feel the fans just above the LEDs. The fans look a decent size, but not powerful enough.
The guy at the lfs
said I could leave the hood off but it looks pretty ugly with lights, cords and everything like that.
The LEDs run cool to touch when I have the hood off but get hot under the hood. They sit on the tank cover with a bit of a gap so perhaps that doesn't help but with the hood on seems to be where they heat up. The hood space is not huge, there is perhaps an inch gap between the top of the LED
unit and the hood.
I might be able to mount a fan at the back on the underside of the hood to draw air in.