LED Light Cooling

[Cave Dweller]

I've got 12 LEDs mounted in a nano hood to a 9x4.25" heatsink. Do I really need to have some sort of fan blowing over it for additional cooling or will it be ok as is? I have a dc blower fan (55mm) right now mounted to a spare screw mount and the thing sounds like it's going to take off!

 

[Cave Dweller]

Bump. Anyone have an idea? Or perhaps a way to silence it a bit? Plastic canvas over the intake? Dont' want to risk some sort of fabric getting in there as the last thing I need is a fire for something stupid. Even considered once of those fan speed controllers but i'm trying to keep everything under the hood and away from as much water exposure as possible (even for being inside the hood).