How close to water do t5 bulbs need to be?

Just as the title says, I am wondering close my bulbs need t be to the water. My current fixtursulte has them between 3-4 inchs.
I am working on designing a canopy that I am going to use an icecap retro kit and I am trying to figure the height of the canopy.
Do the bulbs need to be that close to the water to get the best results?

I would like to have them a bit higher ( maybe closer to 6") to make it easier to get into the tank when I need to.
There doesnt seem to be any real spec info that I can find. Any personel suggestions or experience?

 

like you said my fixture has legs and it set about 3" from the water, not sure if you could go any higher without any problems?

 

I don't think there is a set "rule" on how high above the water the lights should be. However, mine and most are 2-4" and some have theirs right on the glass. Halides seem to be placed a little higher. There is a point, 6-8" I'm guessing, when lights like T5s will lose some concentration and thus intensity.

Maybe Dr.Frag (or other light guru) will chime in.

 

I agree with UncleJed. It depends on how deep you tank is, what you have in the tank, heat buildup, whether you have a protective shield over the bulbs and type of fixture. There's no set height, whatever works. If you notice your corals bleaching a bit or losing color, try raising the fixture. If your tank is getting too hot, raise the fixture. If you don't have a protective shield raise the shield. Just experiment for the best results for you tank.