Difference between normal household FL lights and aquarium lights.

[illumnae]

That is why ADA put green spectrum on their light bulb, for color rendering

But if you look at the graph for arcadia, there's a peak at green too. same for the osram

[Shadow]

On other brand, the green spectrum start at ~500nm. Arcadia start at ~450, 520nm is yellow. Either I'm color blind or Arcadia color spectrum is shift. If you corect the shifting, you should see that blue and red are dominant compare to Osram light spectrum.

[CK Yeo]

"Inefficient" bulbs that grow plants nonetheless at a fraction of the cost? I will go with that anyday. Inefficient in what way? Let's see some real data. I agree if we are comparing between different systems i.e. incandescent bulbs vs FL or CF.

Specialized bulbs cost 5-10times more than household daylight bulbs. Even if plants photosynthesize at 80% of their maximum, so what? Sure, maybe it is not *optimum* but I can live with that.
I think Diana Watsland did some comparsion and there are some real data on this. Does anyone have it off their fingertips?

Agree on changing regularly. If their spectrum is off, their intensity would have faded too. Not so sure about UV though. Plants worry about getting tanned? Plants have their mechanisms to protect themselves from UV radiation. Are cheap bulbs giving off enough UV for us to be concerned?

Yes, ADA bulbs have a greenish tint to it. Yucks. Again, personal preference.

ck

[Shadow]

by the way, is there any study on the impact of the bulb life time and plant growth? Will the plant grow slower or it die off? and when you change to new light bulb, does the plant able to adapt immediately?

[Philosophos]

First I will say that UV is a concern because of algae growth stimulation. UVA is what we're dealing with. Previously thought to be harmless, it's turning out to be more and more dangerous to humans. But that's besides the point. UVA is something algae uses, and is stimulated by far more than plants:
http://cat.inist.fr/?aModele=afficheN&cpsidt=14153234

Compare PAR:
http://www.efn.org/~k_mccree/Professional/FigPAR.jpg


So with that out of the way, here's my comparison of lighting type.

I'm going to keep pics in links, otherwise this will turn in to one very long thread. I'm also going to be using coralife since it's a popular brand around here that I can find good graphs for. I wish there were better ones of sunpaq online; they make a superior light IMO.

First off, I'm taking regular incandescent off the list. They get fewer hours of light, and they use a lot of power. Check out the chart:
http://upload.wikimedia.org/wikipedi...tbulb_type.svg

While lumens != milimoles, the spectrum offered by CF and regular fluoro are obviously superior, and the cost is far lowwer.

Next, lets compare price of fluorescent vs. compact. I'm going to use google's shopping search to find the best prices possible, so that it's verifiable to all of us. I'll be using bulbs suited to a 24'' tank, since that seems to be the standard around here.

Here's Coralife's 6700K CF:
http://www.google.com/products?q=21%...+compact&hl=en

Here's Sunpaq's 6700k:
http://www.google.com/products?q=sun...+compact&hl=en

I find a reasonable price to pay is about $25. I can buy either one at the same price around here in a retail store. On sale, it'll go as low as $20.

So a CF 21'' 6700k bulb costs about $0.384/W or as low as $0.308

Coralife's regular 24'' fluorescent:
http://www.google.com/products?q=24%...orescent&hl=en

The going rate is usually about $10-$15 in my experience: $0.417-$0.625

Regular household fluorescent:
http://www.google.com/products?q=24%...orescent&hl=en

Prices are usually $7-10 around here for a 20W 24'' That's: $0.292-$0.5

The regular spirald compact fluorescents:
http://www.google.com/products?q=65w...orescent&hl=en

$20 seems a fair price. I'll ignore that cheap german specialty CF for plant growth for $16 to be nice

65w @ $20 = .307

So then, the comparison between CF and regular prices around here isn't much different. Between what I find on sale, plus the extra time and cost of rigging/modifying a ballast, etc. I might as well have gone with a CF. The spiraled CF have a pretty nasty spread pattern for rectangular tanks; a lot of light is lost from the circular spread pattern. I also like how CF takes up less room over the top of the aquarium than a row of three fluorescent lights.

Now then, lets compare CF Coralife vs. household fluorescent for spectrum:

Coralife 6700k:
http://i155.photobucket.com/albums/s...C/Colormax.jpg

Cool White Osram:
http://www.coollights.biz/articles/a...ctrum3200k.jpg

3000k General Electric:
http://ledmuseum.candlepower.us/seventh/cflbl2.gif


Look at the 400nm UV, Look at where the nanometers spike. Your prices may be different than where I am, but for me, grow light CF's are much more worth my time.

-Philosophos

[Shadow]

I'll be damn, what do you think of this:

Green Light Drives CO2 Fixation Deep within Leaves

I have not read the whole article, but the title make me re-think my believe

[illumnae]

your colormax doesn't spike at the red spectrum. didn't you say in your first post in this thread that most of the light should be at the blue and red spectrums?

[StanChung]

ADA MH[white]+pl combo's look the best IME.
Grows well enough so no complaints. I don't like the green MH-too sickly looking IMO.

Household bulb like Phillips 865 is quite good for price/performance/colour.

[Philosophos]

I'll be damn, what do you think of this:

Green Light Drives CO2 Fixation Deep within Leaves

I have not read the whole article, but the title make me re-think my believe

Ya, Tom Barr landed this one on his site a couple days ago. It's getting a lot of attention, and I have a feeling my view won't be popular. In any case, here we go:

What's not being accounted for here is what % of the radiation is dissipated in the top 10-20%, and how much of that is green spectrum. Also of interest would be how much additional energy is required to fixate the CO2 vs. the energy used in the upper layers of the leaf.

This again is where I don't think one can contradict PAR; if plants grow better with proportionately less green light, then when would green light within the source be more important? Why would it be advantageous to be non fruit bearing for reproduction and have green leaves, unless carbon fixing requires proportionately less green light?

I also quietly wonder about the differences between spinach and ludwigia

-Philosophos

[Shadow]

Can you share Tom Barr link? would be interested to follow

The journal isn't free

[Philosophos]

Can you share Tom Barr link? would be interested to follow

The journal isn't free

He links to the exact same page in the thread:
http://www.barrreport.com/general-pl...light=fixation

And then some other paper. The other paper seems to show longer shoot length under green light, but less branching and wet/dry weight, which is kind of what we're after.

*edit* the whole article and its discussion has annoyed me enough to leave a post on the site asking about it.

-Philosophos

[illumnae]

My brief unscientific test:

When I ran 2x 11w Arcadia tubes, my HC started pearling ~4 hours after lights on. Today, I switched to 2x 11w Philips 865 tubes and my HC started pearling 1+ hours atfer lights on.

Don't know if it means anything, and I probably missed out alot of controls, but that's my layman observations

[boxedfish]

a question. let's say i have a choice of 2 PL tubes with choice of 6500k or 4000k or 3000k or 2700k to choose for my planted tank, which tubes should i use? should i mix and match with different k or use same k tubes? hoped to have some suggestions.

[StanChung]

He links to the exact same page in the thread:
http://www.barrreport.com/general-pl...light=fixation

And then some other paper. The other paper seems to show longer shoot length under green light, but less branching and wet/dry weight, which is kind of what we're after.

*edit* the whole article and its discussion has annoyed me enough to leave a post on the site asking about it.

-Philosophos

This is no surprise. Amano has said while diving in the blue green depths of the sea where there are corals, he noticed photosynthesizing corals. He took some light measurements and what not. That's part of the idea for his 'green' lighting other than making it look greener/fresher. Of course I'm oversimplifying.

[StanChung]

a question. let's say i have a choice of 2 PL tubes with choice of 6500k or 4000k or 3000k or 2700k to choose for my planted tank, which tubes should i use? should i mix and match with different k or use same k tubes? hoped to have some suggestions.

Stick to the 6500K's if they're very white.
The warm colour of the other tubes are not pleasant for a planted tank. Makes all the 'vegetables' look yellow and wilted.

[boxedfish]

Stick to the 6500K's if they're very white.
The warm colour of the other tubes are not pleasant for a planted tank. Makes all the 'vegetables' look yellow and wilted.

thanks for the input