How high should be distance from water to a bulb

[sasha]

Hi Guys,

The closer I am to filling my 30G tank with water the more questions pops up. The most annoying probably about lighting. The canopy that comes with it has only 2x20W, so it looks like dungeon with both bulbs on Originally I was thinking to buy a Hagen ballast kit Glomat2 (2X20) and add two power glo to it. But after looking at the tank's pics here and in the pet store I became concerned about this idea. Most of the tanks has a lighting unit standing on quite a distance and on stands without covering the whole tank like a canopy that I have. And I am wondering that if I add somehow two additional bulbs they will be close to the water surface than the built in are. Would it be a problem, salt water is quite a good conductor? And what is the appropriate distance between water and a bulb?

Thanks!