# Glass Tops?



## Udenlo (Feb 10, 2011)

I was just wondering if glass tops on aquariums have any ill effects on lighting and plant growth.

Thanks 
Udenlo


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## vancat (Nov 5, 2004)

Yes, they do cut down on light, even more when dirty or covered with condensation. Over time, deposits build up and cut down light even more. After a few years, the glass becomes etched and you can't clean it at all. UNLESS you are very diligent with cleaning it with vinegar....which i wasn't....I switched to open top & LOVE it.


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## Udenlo (Feb 10, 2011)

Awesome, thanks for the reply. I guess I'll just throw mine in the closet then lol.


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## vancat (Nov 5, 2004)

don't throw it, it's glass!!


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## juantoro (Feb 25, 2010)

Has there ever been a study on exactly how much a glass top affects the amount of light reaching the plants? I have fish and/or shrimps in all of my tanks and would never feel comfortable not having glass tops for fear of finding my friends on the rug when I get come home from work.

But, for instance, if one knew that a glass top causes a 20% reduction in light, could one then compensate by increasing the wattage, or putting the light closer to the glass? Or doesn't it work like this?


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## Seattle_Aquarist (Mar 7, 2008)

Hi Udenlo,

The effect negative effect may be substantially less than is being suggested. Here is a post I did in response to a similar question on another forum. The results are based upon quantitative data.



> I responded to a similar question on another forum in this thread. The results were interesting. It was a standard 30 gallon (36" length) with an 2X36 watt (6700K) AH Supply kit over a Aqueon Versa-Top. With new bulbs and no glass top the PAR = 110; with "dirty"* Versa-Top in place PAR = 96; with cleaned Versa-Top in place PAR = 101. All readings were taken with new bulbs @ substrate level about 13 inches below the fixture.
> 
> *dirty = lots of dried water spots on top; some "etching"; condensation; dust


Bottom line, the loss is about 15% with a really dirty, etched glass top and about 10% with a clean, reasonable clear glass top.


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## spypet (Jul 27, 2007)

even though I don't use a tank cover, I do keep one in storage for long vacations,
since the cover cuts the water lost to evaporation during my absence by 70-90%.
it also comes in handy when I have a lot of party guests over and I don't want any
curious hands, pets or foreign objects getting into my tank.


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