How high is the hunging light?

[Wes888]

My lights consist of 2x150W HQI and 2x130W Actinic compact fluorescent. I'm going to mount a couple of 120mm (4.7") PC Case fans on the edge of the tank. In order to make room for the fans, I have to hung the lights 7" off the water. Is it too high? Should I use smaller fans and hang the light lower?

The supporting legs that came with the light assembly was only 2.5" tall.

 

[ndepratt]

this is a complete fixture, correct? are you having issues with temperature at the moment?

I really wouldn't raise the fixture higher unless you've exhausted options. have you considering having the fans on the back of the tank blowing diagonally?

if you have a sump I would recommend putting the fans on the sump.

 

[Wes888]

Yea, it's a complete fixture. When I was using the supporting legs that came with the unit, even using a 12" Vornado fan didn't help on a hot and humid day. Yote suggested raising the fixture a few inches and it helped big time! Since the light fixture is higher now, I almost have enough room to mount a couple of 120mm fans instead of having a loud and ugly fan sitting few feet away from the tank blowing at it.

Is having the light closer really help that much? I can understand water depth could block out the light energy due to the energy absorption coefficient, but light in the air is negligible. The other thing that I was considering was the light reflector. It could have a focal point at certain feet down. But even so, off by 4-5 inches should not make that much a different on a 3 feet deep tank. That's all just physics, but I want to confirm it with your guys to see if anyone experienced any problem with the light hanging high and caused problem.

 

[project5k]

energy emmission and transmittion is is equal to the inverse square of the distance, increase the distance, and loose a measureable about of the light energy making it to the bottom of the tank, even tho it is just air gap your adding...

not to mention that there is a greater chance of some of your light leaking out over the edges of the tank the higher you go, and that adds to your losses...

 

[yote]

I dont think I would raise the light that much.
Mines just 4 1/2" above the tank rim,I wouldnt go 7.

 

[Wes888]

mine is at 4 3/4" above the tank rim as well. That's exactly 120mm and it can fit the fans. "Almost" 7" is above the water.