# Too much light?



## mjbn (Jan 1, 2012)

I'm running two 20W 6500k Daylight CFLs over my 20g long tank. 
Here's a picture. I've added a TON of frogbit since this though. I am getting some hair/thread algae or something growing and I've read it's from too much light and high nitrates.


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## Michael (Jul 20, 2010)

I doubt that this is excessive light. These are spiral CFLs, correct? Are they mounted vertically or horizontally? Vertical position gives much more light.


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## mjbn (Jan 1, 2012)

Yes spirals mounted horizontally, no reflectors. Has 10 small holes drilled above each bulb for heat escape. I'm wondering why this algae is appearing then.


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## Michael (Jul 20, 2010)

You probably have low light. Algae growth is caused by many things, and yours is probably triggered by something other than light. Try going through some of the stickies in the algae forum and try to narrow it down.


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## mjbn (Jan 1, 2012)

Really?:O I talked to another person on another forum who knows his stuff really well too, and he said I have too much light.?


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## Michael (Jul 20, 2010)

I could be wrong--the only way to know for sure is to measure it with a PAR meter. But the horizontal placement decreases the light (as measured with a meter) by over 50%. And no reflectors decrease it further. And you say you have a TON of frogbit.

The best discussion of CFLs for aquarium lighting I've seen is at http://www.plantedtank.net/forums/lighting/85667-par-data-spiral-power-saver-bulbs-2.html


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## mjbn (Jan 1, 2012)

Thanks for the link! I'll probably try out a PAR meter since a local club is passing one around for free


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## nakigara (Feb 5, 2012)

Although I think that is a really great post with a lot of good info (it pretty much convinced me to give up on trying to wire a t5 electronic ballast and just screw in some CFLs into shop lights) - I do think people confuse bulb orientation with the reflector issue.

That posting (if I remember correctly) doesn't compare the bulb in vertical and horizontal orientations with the same reflectors- I took it to be comparing very different reflectors.

If you don't have a good reflector, I'd hazard a guess that a horizontal CFL orientation would get more usable light to the substrate, since more of the tube's surface area would be facing the substrate unobstructed. In a vertical orientation, very little of the tube would be facing the substrate, most of the light from the spiral would either have to pass through other layers of the spiral (loosing intensity, etc.), or be dependant on bouncing off of the reflector(where reflector quality comes in) to reach the substrate.

but, if you can get a par meter, and do some experiments, that would be the best. try to only change 1 variable at a time (i.e, height, orientation, wattage, reflector, etc.) and keep all other variables identical.

good luck


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