# Cool Light "GE" and Algae



## newbie314 (Mar 2, 2007)

The tank is having a little algea growing on the right side of the tank (where the light is stronger). I may need to switch to a cool light "GE".

What is equivalent for this type (using compact flores.)?
I'm using Marine land compact that is 5100K. Is this equivalent?
Wondering is I could just put some smoked glass colored plexiglass over the right to reduce some of the light.

How about putting some green plexiglass to get rid of the higher frequency light (that algae likes)?


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## sb483 (May 29, 2006)

From Diana's book, algae can adapt to most light spectrums, so I doubt the green plexiglass would help. Also from the book, plants are worse at adapting to new lighting schemes than algae, so periodic changes in lighting could hurt the plants without significantly altering algal growth.

If you're keeping water changes minimal, and you have a large quantity of growing healthy plants, then eventually I've found the algae stops growing on the glass. I think Diana's book attributes this to alleochemicals building up in the water and preventing algae from growing. Until then, just scrub it off.


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## sb483 (May 29, 2006)

That book, btw, is _*Ecology of the Planted Aquarium*, Diana Walstad_. If you haven't yet, I highly recommend you have a look. The chapter on Algae discusses how most species can adapt to nearly any light spectrum.


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## newbie314 (Mar 2, 2007)

Yes I have it.
I actually was refering to section where she mentions switching to Cool-light.
Also in the same section a scientific descprition of perfered wavelengths for Algae. Something to the affect 520nm below algae really like. Made it sound like the plants wouldn't mind the change in wavelength or at least way less than the algea.

I'm trying more emergent plants and the anacharis. I'm keeping a look out on the Vals. I think me clearing out the right side for the values is causing too much light in that area. I think I should have brought up my moss closer to the surface, because is has some algae on top. Maybe I should just add in what I took out. I'm going to try and make some of the moss come out of the water and see what that does.


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## littleguy (Jan 6, 2005)

So-called "Cool-white" is usually around 4100K.
"Warm-white" is 2700K I believe.
"Daylight" bulbs are usually ~6700K.
I've seen a few "Sunlight" bulbs that are around 5000K.

It can be difficult to find the Kelvin rating on many off-the shelf bulbs, but it's usually on the packaging somewhere if you look hard enough. Sometimes the K rating is not labeled specifically, but the model/serial number will give you a hint. For example it might contain the numbers 27 (2700K) 41 (4100K) 50 (5000K) 67 (6700K) etc.

I think that was your original question anyhow.


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## 01krisp10 (Feb 18, 2007)

I posted my question about bulbs in my 20H journal. Forgot this thread was going. Basically I came to the same conclusion, remove any bulbs that peak in wavelength below 520nm on the spectrum. I have Colormax bulbs in my 20H and my 5g, they are both coming out as they have peaks at around 400-420 I think it was. I just need to find a replacement, Walstad recommends the cool-white light as newbie314 mentioned.

The problem with choosing a light based on its spectrum is that you don't know where the peaks are, any clues on how to figure this out littleguy?


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## littleguy (Jan 6, 2005)

01krisp10 said:


> The problem with choosing a light based on its spectrum is that you don't know where the peaks are, any clues on how to figure this out littleguy?


No I don't. But it kind of doesn't matter. Even if you know the optimal wavelengths and so forth, you are limited to only a small set of bulb phosphor combinations that are actually available that come close to the theoretical optimum. They are the 4100K, 5000K, and 6700K bulbs. Walstad's data in her book suggests that 4100K is best, while most high-tech folks use 6700K, and many other folks split the difference and use 5000K bulbs with great results.

I would just use whichever one looks most pleasing to your eye, or is easiest to find, cheapest, etc. All three are a safe bet. The 6700 is ever so slightly bluish, the 4100K is ever so slightly red, and 5000K is probably the purest white. But once you get some tannins and dissolved organics in the water, I find in my experience that the apparent blueness in the 6700K bulbs vanishes and the aesthetic differences lessen. But you may have a more discriminating eye, so see for yourself.

Hope this helps.


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## 01krisp10 (Feb 18, 2007)

Thanks, found a 5500k bright white spiral bulb for my 5g, looks much better than the Colormax (too red) and I hope doesn't have the 420 peak. 

I also purchased a another fixture without the Colormax bulb, and ordered a 10k bulb to replace the actinic one in the new fixture. I'll still have one Colormax, but I'll have 2x 10000k and one 6700k Plant bulb.

Update: Ordered another 6700k Plant bulb to replace the Colormax, I really don't like them.

Ugh, think I just confused myself, lighting is a workout.


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## littleguy (Jan 6, 2005)

Well it shouldn't be a headache. Like I said, any of those in the range 4100K to 6700K are proven winners. The 10,000K might not give quite as good theoretical performance, but then again some folks have had good luck with them too (e.g. TeutonJon's aquacube journal).

Bottom line, if you find something that works, and you like the looks, stick with it.


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## TeutonJon78 (Nov 10, 2004)

I've people using stuff all over K range and get it to work (check out the lighting forums in any of the plant forums). Some people are even using the MH lights at 14k and 20k. Remember that it's the spectrum that plants care about, not how it appears to people. That is why the plants bulbs look purple...good for them, no so pretty for us.

I think plants like the blue spike, but so does algae and hence the problem of out competing the plants for whatever reason.


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## 01krisp10 (Feb 18, 2007)

Well the plant bulb I have is actually white/green. The Colormax isn't really touted as a plant growth bulb.


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