Got a good explanation of color temperature, spectrum, etc?

Hi All,

Other than making it bright enough and with a reasonable light color to show off my fish well, lighting is somewhat of a mystery to me. I sort of understand the wikipedia article on color temperature (Kelvin) at http://en.wikipedia....lor_temperature, but the diagrams under "spectral power distribution" (http://en.wikipedia....er_distribution are by far the most clear. I wish that when you went to buy a bulb you'd see a diagram like that on the package, instead of just the color temperature, "full spectrum", whatever. The best would be if it would give you a chart like that that had actual power output on the Y-axis -- I guess the measure of light output for each wavelength would be irradiance (http://en.wikipedia....tral_irradiance)?

Thus far, I've gone with very cheapo DIY lighting solutions: 30W total of compact fluorescents (spiral bulbs in regular sockets) in reflectors in the custom hood for my 29g tank, 4' shop light with two standard T8 bulbs over my 75g tank, and a 2' 2800K T8 bulb in a 37g tank. Without knowing anything about the color temperature of the compact fluorescents, they seem to do the best job of getting plants to grow of any of my setups. But... I'd like to really *understand* what I'm doing with all this. Sure, there's *tons* of info out on the web, but it's hard to separate out who really knows what they're talking about, and who's just repeating back what the 16 year-old at PetSmart told them.

I seem to remember Todd Crail (farmertodd) posting a series of pretty detailed explanations of the various lighting terms / options back in the NANFA-L e-mail list days. Todd, any chance you still have that and could repost?

Skipjack posted a link to an interesting article at http://aquaticpredat...showtopic=31948 about mixing different fluorescent bulbs to get a good spectrum, but there's a bit much jargon there and not nearly enough explanation about what each type of bulb is accomplishing.

I tried doing my own searches on the forum, but didn't have much luck. Not sure what specific terms other than "lighting" I could use.

Can anyone actually explain all of this, or point me to a detailed explanation elsewhere on the Forum or the web at-large?

Thanks, Jase

It is possible to overanalyze these things. I used to be obsessed with color temp, spectral characteristics, etc.

No more.

Driftwood and rocks don't care what kind of light you have.

I hear you, Irate. But... I do want to have some plants, and I want to learn enough that I can tell what DIY solutions will work, and which are just wrong spectrum, etc.

-Jase

Here's my advice - it's what I did after casting aside all the technical mumbo-jumbo:

Get a 10 gallon tank (or two) and experiment. It's a LOT cheaper to do DIY experiments on a small scale. You will learn a lot along the way.

I have a bit of experience in this department. I have used many spiral compact flourescents in my 10g's to grow plants. Those pinkish Colormax bulbs seem to do very well though I haven't tried any basic CF bulbs from the grocery store yet. In my experience though, anything between 5000k and 10,000k is good for plants. When I first started I inherited a Current 30'' single tube fixture with a 50/50 bulb in it. It DID grow my plants, however, the algae seemed to love the blue light. I will also attest to this when I bought my metal halide fixture pre-loaded with 14,000k bulbs. My tank pretty much looked purple, and I had very little plant growth and LOTS of algae growth. Good thing I had a saltwater buddy that would buy the bulbs so I could afford to buy new 6,700k bulbs. I'm much happier with the results.

In a nutshell, my advice: Get lights between 10,000k and 5,000k, with 6,700k being my personal favorite (a tiny bit yellow looks natural to me, 10,000k is about pure white, but that's your preference) and most plants do fine with 1.5 watts per gallon, but for good growth do 2.5 or more. If you want low maintenance with plants that will do well but now grow out of control, go for around 2 watts (though this varies with tank depth among other things, and is an entirely different tip of a whole other iceberg)

Edited by Kanus, 17 March 2008 - 09:29 AM.

I have used many spiral compact flourescents in my 10g's to grow plants. Those pinkish Colormax bulbs seem to do very well though I haven't tried any basic CF bulbs from the grocery store yet. In my experience though, anything between 5000k and 10,000k is good for plants.

I tried using a walmart bought sprial CF in addition to my regular light strip and it just gave the tank a wierd yellow glow. Can you find color temperature on CF and have them NOT give off a yellow glow?

Andy

I tried using a walmart bought sprial CF in addition to my regular light strip and it just gave the tank a wierd yellow glow. Can you find color temperature on CF and have them NOT give off a yellow glow?

Andy

I pick bulbs based on what gives good color rendition. To me, the most pleasing spectra are those that rend the colors of my stock the most honestly. Also, these spectra seem to fall in the general range given as "good for plants."

To my eye, a CF with a color temp below 5000K is too yellow, while more than 10,000K is too blue. My current setup is a mix of 6700K and 9325K, which is pretty neutral in terms of color rendition. If I only run one or the other bulb I it looks off.

Basically, I would pick bulbs that look good to you. Good call on the 10 gallon tests. I build pin type 13w PC rigs for tens for about $15 a piece. Here's a link. You can find a wide range of cheapo bulbs for them on eBay if you want to play around. If you want to keep it simple, just shoot for somewhere in the middle of the range.

I think light intensity, photoperiod, and water clarity are more important than color spectra when lighting planted tanks. But if you do step up the light intensity with CF, then you will have to start looking at a whole other mess of variables (like fertilization).

But on the spiral CF can you actually find the color temperature? I have looked and it doesn't seem to be listed on the box. Do I just have to really look into the fine print to find it? Even looking the bulbs up on Lowe's website doesn't give color temperature of those bulbs, but it does for regular flourescent tubes.

Andy

But on the spiral CF can you actually find the color temperature? I have looked and it doesn't seem to be listed on the box. Do I just have to really look into the fine print to find it? Even looking the bulbs up on Lowe's website doesn't give color temperature of those bulbs, but it does for regular flourescent tubes.

Andy

Sometimes, but not often. I think you can make a reasonable guess based on the qualitative term -- soft white, cool white, etc. I have seen charts online that give the general temp ranges for these colors. So-called plant/aquarium bulbs will have a decent color but a lousy price. Mostly, screw in CF = yellow.

I don't use spiral CF much these days because of restrike - much of the light and heat produced has nowhere to go. I think a pin type 13w PC with a good reflector is worth two or three screw in spiral lamps, and uses half to one third the electricity. But then again I have a terminal inability to KISS.

Unfortunately, color temperature really isn't the issue you want to be looking at. All color temperature means is what the light looks like to the human eye. It doesn't tell anything about how much of the different spectra is available. What you really need to know is the PAR of the light - Photosynthetically Available Radiation - the light that is used by the plants. BUT... this is never listed. So we have to make do with other measures.

The wavelengths used the most by chlorophylls a and b are in the red (620-640 um) and blue (405-440 um) range. Carotenoids collect some of the more greenish light, but not as much as chlorophylls a and b. The best thing I've found to do is to go to the manufacturers website and see if they show the spectrograph of the light.

During a quick google troll for better discussions of PAR, I found this: http://www.sunmaster...tandPlants.html

Otherwise, the best discussion of aquatic lighting science I've seen so far is here: http://www.aquaticpl...tosythesis.html

Lastly, if you want to get into the nitty gritty of understanding how photosynthesis works, I found this:
http://www.emc.maric.../BioBookPS.html

Unfortunately, color temperature really isn't the issue you want to be looking at. All color temperature means is what the light looks like to the human eye. It doesn't tell anything about how much of the different spectra is available. What you really need to know is the PAR of the light - Photosynthetically Available Radiation - the light that is used by the plants. BUT... this is never listed. So we have to make do with other measures.

The wavelengths used the most by chlorophylls a and b are in the red (620-640 um) and blue (405-440 um) range. Carotenoids collect some of the more greenish light, but not as much as chlorophylls a and b. The best thing I've found to do is to go to the manufacturers website and see if they show the spectrograph of the light.

Exactly. Most of the stuff you'll find on the web goes on and on about color temperature, but if you actually look at what that means, it's relatively useless for a fluorescent bulb. The light from a 6,000K fluorescent bulb might *look like* the light from a 6,000K black body to the human eye, but that doesn't mean it's the same thing at all. Like I said, I'd love to find a source that has diagrams like those at http://en.wikipedia....er_distribution for different common lights -- so you can see how much of the light is in the wavelengths actually useful to plants.

I guess ideally you'd want to do is find a bulb where the spectrograph roughly matches the PAR graph which nativeplanter linked to at http://www.sunmaster...Response_01.jpg

I guess ideally you'd want to do is find a bulb where the spectrograph roughly matches the PAR graph which nativeplanter linked to at http://www.sunmaster...Response_01.jpg

...and in a lot of cases that means making the graph yourself, as this data is not generally available. There are more fundamental issues when it comes to getting the most from your lighting. Great thread, though.

This site has a number of spectrographs, although it is getting a little outdated I think: http://www.geocities...37/spectra.html

Here's another site with some limited, but very good info with spectrographs: http://ledmuseum.hom...et/spectra7.htm

I'd love it if someone could do a spectrograph on the new Ott-Lites I've been using. I don't have the equipment.

From what I hear, bulbs that have optimal spectral characteristics for plants are also great at growing algae. Plus they look purple.

Another measure of color temperature is CRI, or Color Rendering Index. A CRI of 100 mimics noonday sunlight.

I like bulbs that look natural. Get enough of 'em and you don't have to worry about things like spectral output. You can mix and match too! Phillips "Daylight" bulbs at about 6000K do the trick for me. At least, my driftwood, rocks, and plastic plants think so.

I seem to remember Todd Crail (farmertodd) posting a series of pretty detailed explanations of the various lighting terms / options back in the NANFA-L e-mail list days. Todd, any chance you still have that and could repost?

I emailed Todd, and he no longer has this email available. Does anyone have an archive of the nanfa-l messages that might include this email and could re-post it here? I suspect it might be from somewhere between August 2006 (when the archive at http://www.nanfa.org/archive.shtml ends) and February 2007 (as far back as my personal archive of messages extends). As I recall it, it was pretty much a full dump of Todd's (substantial) knowledge/experience with different lighting options at that time.

Thanks, Jase

This might be it - you're lucky I tend to be lazy and not delete things...

Date: Fri, 31 Mar 2006 15:22:40 -0500
From: "Todd D. Crail"
Subject: Re: NANFA-L-- spiral strip

Really, any of these bulbs are good, depending on what your application
is.
It just depends on what you're trying to do. There might be a little
confusion about what either is doing, so I'll try and put this
together.
Hopefully you find it helpful in deciding what you do with either type.

The categories basically boil down to this:

If you want to grow plants, you want a bulb that puts off high
Photosynthetic Active Radiation (refered to now as PAR).

If you just want to illuminate your tank without the radiation
(unplanted
but want it to appear brite), you want low PAR.

But how are they different when you're standing there at the shelf of
the
local home improvement store?

What is radiation when discussing light bulbs? This is a lot of the
"heat"
you feel coming off an incandescent bulb. Yeap, it's not really heat
as you
think of it, like "this room is hot"... Try putting a fan on the light
fixture and putting your hand under it again with the fan running...
It's
still hot, but all the heat should have been blown away, right?

Depending on the "temperature" or "color" of the light, a plant is able
or
unable to use the radiation. That is to say the "color" or "temp"
where the
peaks of colors are in a spectrogram for a given light source (a
spectrogram
being that rainbow colored pointed graph thingie you see on some
packaging).

Plants don't see the whole spectrum like us... If they had eyes like
ours,
they would see mainly yellow and red, and even infared which we can't
see.
So... They're looking for radiation with a yellow or red color, which
they
use to excite cholorphyll and manufacture sugars to "eat". But those
light
colors look like crap to our full spectrum eyes.

Lumens is the overall brightness, no matter the "color" or
"temperature".

And herein lies the trick to understanding this...

You're illuminating a device that has an output of energy (measured in
watts). It has each of these properties we've discussed. However...

The spiral bulbs are what we consider "high efficiency" bulbs are
forced to
emit a more blue color, which requires more energy to emit (different
gasses
to illuminate), BUT, emits very little "lost energy" as radiation that
we
can't see (infared to red). This is where they get away saying
they're
"saving energy" but really, they're not doing much of anything except
giving
a more effective output of the energy input.

They can have the same luminosity as a "less efficient" bulb, but (and
this
is of note) offer absolutely nothing to photosynthetic organisms.
That's
why the spirals work great over fish tanks, as they have very little
PAR to
offer to algae, but don't expect much of them for plants.

What has me jazzed about the Reveal bulbs is that they emit a very
strong
peak in the yellows and reds, yet have been adjusted to also offer
peaks in
the other colors, so it also looks good to my eyes.

Another way to look at it, and this is also why your deeper water
photography looks blue... The blue wavelengths were the only light
waves
that had enough energy to penetrate that deep. Think of the blue
waves of
light as long distance runners. Ready, steady, but wouldn't knock you
over
if they ran into you. However, they could get back up, and keep going
after
the collision.

On the other hand, a yellow or red wave of light is like a sprinter.
Tons
of energy right now, but not much endurance at all. They could plow
you
over, but after the collision, they're not going to run much further,
and
definately not at the rate they were going before they hit you.

Well, that's some thoughts. Hope that helps if you're considering
getting
away from standard output flourescents.

Todd
The You Light Up My Life Madness, Toledo, OH
It's never too late to have a happy childhood.
http://www.farmertodd.com

This might be it - you're lucky I tend to be lazy and not delete things...

Date: Fri, 31 Mar 2006 15:22:40 -0500
From: "Todd D. Crail"
Subject: Re: NANFA-L-- spiral strip

Really, any of these bulbs are good, depending on what your application
is.
It just depends on what you're trying to do. There might be a little
confusion about what either is doing, so I'll try and put this
together.
Hopefully you find it helpful in deciding what you do with either type.

The categories basically boil down to this:

If you want to grow plants, you want a bulb that puts off high
Photosynthetic Active Radiation (refered to now as PAR).

If you just want to illuminate your tank without the radiation
(unplanted
but want it to appear brite), you want low PAR.

But how are they different when you're standing there at the shelf of
the
local home improvement store?

What is radiation when discussing light bulbs? This is a lot of the
"heat"
you feel coming off an incandescent bulb. Yeap, it's not really heat
as you
think of it, like "this room is hot"... Try putting a fan on the light
fixture and putting your hand under it again with the fan running...
It's
still hot, but all the heat should have been blown away, right?

Depending on the "temperature" or "color" of the light, a plant is able
or
unable to use the radiation. That is to say the "color" or "temp"
where the
peaks of colors are in a spectrogram for a given light source (a
spectrogram
being that rainbow colored pointed graph thingie you see on some
packaging).

Plants don't see the whole spectrum like us... If they had eyes like
ours,
they would see mainly yellow and red, and even infared which we can't
see.
So... They're looking for radiation with a yellow or red color, which
they
use to excite cholorphyll and manufacture sugars to "eat". But those
light
colors look like crap to our full spectrum eyes.

Lumens is the overall brightness, no matter the "color" or
"temperature".

And herein lies the trick to understanding this...

You're illuminating a device that has an output of energy (measured in
watts). It has each of these properties we've discussed. However...

The spiral bulbs are what we consider "high efficiency" bulbs are
forced to
emit a more blue color, which requires more energy to emit (different
gasses
to illuminate), BUT, emits very little "lost energy" as radiation that
we
can't see (infared to red). This is where they get away saying
they're
"saving energy" but really, they're not doing much of anything except
giving
a more effective output of the energy input.

They can have the same luminosity as a "less efficient" bulb, but (and
this
is of note) offer absolutely nothing to photosynthetic organisms.
That's
why the spirals work great over fish tanks, as they have very little
PAR to
offer to algae, but don't expect much of them for plants.

What has me jazzed about the Reveal bulbs is that they emit a very
strong
peak in the yellows and reds, yet have been adjusted to also offer
peaks in
the other colors, so it also looks good to my eyes.

Another way to look at it, and this is also why your deeper water
photography looks blue... The blue wavelengths were the only light
waves
that had enough energy to penetrate that deep. Think of the blue
waves of
light as long distance runners. Ready, steady, but wouldn't knock you
over
if they ran into you. However, they could get back up, and keep going
after
the collision.

On the other hand, a yellow or red wave of light is like a sprinter.
Tons
of energy right now, but not much endurance at all. They could plow
you
over, but after the collision, they're not going to run much further,
and
definately not at the rate they were going before they hit you.

Well, that's some thoughts. Hope that helps if you're considering
getting
away from standard output flourescents.

Todd
The You Light Up My Life Madness, Toledo, OH
It's never too late to have a happy childhood.
http://www.farmertodd.com

NativePlanter, that post you linked to is really useful. Is that by our own "Newt"? http://www.aquaticpl...tosythesis.html

I haven't been on the forum much lately because I've been busy with other projects, including getting lots of seedlings started for a summer garden. In doing that, I've built a bunch of setups to suspend standard 4' fluorescents above them. As for bulbs, I found advice in some gardening forums that suggested mixing "daylight" (6500K) bulbs with cool white (4100K). Can anyone comment on that? Would I be better off just sticking with two 6500K bulbs? Since the spectra can vary widely, it does make some sense to me to mix it up a bit to try to ensure I have the important spectra covered...

And has anyone seen any commercial LED solutions yet (not just the moonlight stuff)? I'm pretty convinced that LEDs *will* take over eventually, as it's possible to manufacture them with the exact wavelength desired (at least using phosphor coatings). Imagine a lamp that did only the peaks required for plants -- now *that* would be efficiency!

Cheers, Jase

NativePlanter, that post you linked to is really useful. Is that by our own "Newt"? http://www.aquaticpl...tosythesis.html

I haven't been on the forum much lately because I've been busy with other projects, including getting lots of seedlings started for a summer garden. In doing that, I've built a bunch of setups to suspend standard 4' fluorescents above them. As for bulbs, I found advice in some gardening forums that suggested mixing "daylight" (6500K) bulbs with cool white (4100K). Can anyone comment on that? Would I be better off just sticking with two 6500K bulbs? Since the spectra can vary widely, it does make some sense to me to mix it up a bit to try to ensure I have the important spectra covered...

Not sure, but it looks like a different "Newt". Newt, care to comment?

Anyway, I like the idea of mixing the bulbs better, if for no other reason than I think it will look nicer. Two daylight bulbs might look a little blue and/or washed out. The other bulb should bring out more reds. Even better, I might use the daylight and a warm white. Otherwise, I have been having very good results so far with the Ott-Lite plant bulbs sold at Home Depot for about $9 I think. Sold as T12.