How much does glass filter out?

[DeadlyMuffin]

I was looking at new wave t5 fixtures since they appear to be about at the same price level as dealing with a retrofit kit and a lot less hassle. It looks like they need the tank to be covered. This isn't necessarily a bad thing, with an open top even lights designed for exposure to water will have problems eventually. I'm just wondering how much a cover would reduce the light to the tank.

Does anyone have figures on how much a glass cover reduces the light that gets to the coral? I'm also trying to find if there are different types of glass that may be better or worse.

For whatever it's worth, the light would be for a 30" tank (29 gallon) and I was looking at the 24" 4 bulb or 8 bulb model. Not planning on SPS or anything, but it would be nice to maybe be able to keep a BTA so leaning towards 4 bulbs.

http://www.sunlightsupply.com/aqua/...NW_T5&title=Fluorescent Lighting&type=product

edit: I know MH can be done on a real shoestring too, but I figure T5 is a lot better on the power bill.

 

[luther1200]

I had the glass top on my tank for 1.5 yrs. I finally got tired of cleaning them everyday and got the egg crate. And the brightness was noticeable right away. I never realized how much light they blocked, and I cleaned them all the time. Not only the light but the color even looks better. Once some of that salt gets on there its almost impossible to get off all the way.

 

[DeadlyMuffin]

That makes a lot of sense. Egg crate wouldn't really do much to keep water or salt off the light fixture though. Maybe if you just kept it high enough to be out of range of droplets?

 

[luther1200]

I do get more salt on my fixture now. But its 5-6" higher than the glass was so its not even close to as bad.

The glass will be O.K. just be prepaired to clean it often. I never tried but if it gets bad maybe soak it in vineger.