6700K, 10000K, Actinic...

[Mzungu]

Okay. I know we have a couple hundred posts about this, but I would like to have a thread focused on just the K rating and when to use what.

In one of the other threads, Scott said, in a few posts:

If in fact the lights are 10k, they aren't emitting enough light in the useable spectrum and your plants are basically starving for light. Plants need light in the 6500 to 6700 range in order for photosynthesis to function properly. While the 10k lights look good to us, they are nearly invisible to plants.

as for the 10k lights mary beth, they are good for corals, along with the actinic bulbs, but for regular fresh water plants, not so good. The 10k simulates the harsher light experienced in open water, whereas the 65-67k simulates the more filtered light which reaches fresh water plants. Another reason why MH lights are so popular for coral tanks, the harsher light is needed by the corals, the same light is ignored or detrimental to fresh water plants, often stimulating nothing more than algae growth.

First of all, why is the light reaching FW plants more filtered? Does it have to do with the clarity, bottom material, composition, etc? What about a natural spring, whose water is crystal clear? Am I just confusing myself?
What is an actinic bulb, really? Because there are bulbs out there that says 7100K blue...does that mean actinic, and that one who has a FW planted tank should stay away?
What about brackish water? There are only a handful of actual vascular plants that grow naturally in brackish water (I have some Ruppia maritima in mine). Should I stick with 6700K?
I guess I just don't understand why corals can use actinic bulbs where FW plants cannot...surely the higher-light plants can benefit from...uhh...higher light...?  I'm assuming that if, in nature, they need higher light, then the sun is penetrating pretty well.  :?  
Would using 6700K lights be pointless for a reef tank?
Is it all a conspiracy? I mean, earth revolves around one single light source...Why can't you have one kind of bulb that is beneficial for everything? Is it because, for instance, the actinics are tailored to penetrate deeper than the sun would normally, allowing us to keep corals? Or do corals just look better that way? If sunlight is more filtered in FW, wouldn't your light be more filtered over your FW tank?

Help!

[SCOTT]

Re: 6700K, 10000K, Actinic...

Perhaps I over simplified things to much in my earlier posts. Let me try this again. Fresh water plants have different requirements than corals. This is reflected in the useable spectrum of light, 6500-6700 for fresh water, actually, as low as 5500 can be used, and 10k and actinic light for corals. Each spectrum promotes different reactions in the respective target species.
The actinic light in a reef tank is used to stimulate algae growth which in turn feeds the coral itself.  The 10k's primary function is to wash out the visible blue light from the actinic, and to promote vitamin D production.
Again, oversimplified, but you get the jist of what I am trying to say I am sure.
In answer to the question of brackish vs salt vs fresh, all plants benefit from 6500-6700k light, its corals that we are specifically speaking of that require actinic and 10k light, not the plants themselves.
Did I just make things worse?
As an afterthought here, why is actinic neccesssary rather than plain old 6500 light? It has to do with the visible and non visible spectrum of light. As light passes thru water, it is stripped of the red spectrum of light faster than it is of the blue spectrum. The algaes that the coral have come to depend on for food have adapted to thrive in the blue light spectrum. Thus the need for actinic light.
Oh, something else I just thought of. Did you know that glass, unless specifically treated will filter out 95% of the useable UV? Just an interesting aside for those of us who use a glass lid on our tanks.

[eklikewhoa]

Re: 6700K, 10000K, Actinic...

Not sure of all the technical stuff but there has been lots of discussions that have explained it in other forums.


Plants can and will grow nicely in anything from 5000k-10000k, 10000k is a bit more blue to the human eye but it still produces a good light for plants not as good as something a bit warmer....6700k but it works.

Right now there are lots of people with first hand experience stating that 9325k is perfect for human viewing and plant growth and right now it grows lush green algae in my tropheus tank. ADA sells 8000k bulbs and who wants to argue with Amano? obviously it works if not he wouldn't be able to sell them as he does.

Being a bit of a reef noob but I will say that I research to my limits before jumping into something. Corals will actually do better in similar kelvin light as plants do and actually most have reported that the growth is better with those bulbs.....it's the color that gets lost with the 6700k-10000k. The only thing Actinics do from what I see is supplement blues which make everything look all pretty and stuff. On the same note plants use blue spectrum as well(stem growth I believe) but not as much as the other colors.

Kelvin is just color basically not something really to judge by but only cheap way to go by.....Lux/par is a much better measurement of what works. Kelvin is just the sum of various wavelengths produced by the bulb and you could have two different brand 10000k's and the actual spectrum peaks will be different. A rough estimate of what to use.....a round about.

[eklikewhoa]

Re: 6700K, 10000K, Actinic...

Forgot to add..... for the ultimate viewing/growth combo I would go with 6700k+9325+10000k!!!

[wvgdiscus]

Re: 6700K, 10000K, Actinic...

This is one discussion that can go on & on & on.
For me in my simple little mind what it boils down to is.
What do you want as far as growth & what looks good to you eye.

If salt water corals growth you will want the higher end of the Kelvin as high as 20,000K MH. Now they have come out with the T-5s that can get close to the MH without the heat. This is for deeper tanks. Slow growth takes 10,000K
the Artinics are just  to supliment the colors of the corals.
Like Scott said in the water the red of the spectrum will disappear in just a short amout of depth.

For as fresh water goes agree with what both Scott & eklikewhoa   have said.

[eklikewhoa]

Re: 6700K, 10000K, Actinic...

actually from what I have read with corals it is similar to that of plant growth...they do better with the 6700-10000k but the colors look better with the higher K-rating since there is more blue in it.

Also most tend to not like the 20000k depending on brand since there is low par with most which has little beneficialness to corals.

[wvgdiscus]

Re: 6700K, 10000K, Actinic...

It could be I have it backwards.
I will have to do my research again. As it has been awhile.
Maybe that is why on my T-5 setup I have 10000k & 20000k with actinics in it.

Like I said simple mind. Need something do my research then forget about it.
Unless I use it all the time.

[Mzungu]

Re: 6700K, 10000K, Actinic...

Okay, I've gathered my thoughts now.  :)

So our main concern with corals is to get useable light to their photosynthetic algae? Does algae use a different spectrum of light than vascular plants?

I think one of the hangups I have concerns the lighting as it applies to us. I really don't care how it looks, I would much rather have it be beneficial to the plants in my tanks. Like Walter said, it boils down to what you want as far as growth and what looks good to you - I don't care about what looks good to me.  :)  I'm just wondering what the plants need.

I know it's been discussed umpteen times everywhere, but there are so many different opinions, and I don't understand why opinions would matter, you know?

So, I think, well, at least, what I'm getting from your posts is that photosynthetic algae benefits from the blue-er end of the spectrum, and plants from both blue and red? That's consistent with what I learned a couple of years ago, so that's good. I think where I got lost was in the assumption that Kelvin somehow reflects (oh, bad word for a lighting discussion, sorry) what the spectrum of the bulb is.

I'm still a bit confused, also, on what an actinic really is. Is it just a light with peaks in the blue spectrum? Is there a K value recommended for actinic? (I'm now remembering my first shopping trip to get lights for my new plants, and having to spread out all my options next to eachother so I could compare their spectrums...) For plants, you want peak in the red and blue, correct? Does that correspond at all with Kelvin?

If I'm tiring anyone (sorry if I am!), just feel free to post a link to a thorough yet succinct, readable, and accurate article.  :wink:

[Mzungu]

Re: 6700K, 10000K, Actinic...

Oh, one more thing, since Scott mentioned it...Do vascular plants and/or algae use UV? I hope that's not an utterly stupid question.  :?

[Mzungu]

Re: 6700K, 10000K, Actinic...

:sniff:

[Mzungu]

Re: 6700K, 10000K, Actinic...

Well, I found this thread while looking around. Good to know I can answer most of my questions now!

I wanted to find a place to post a little comparison I stumbled across when posting on edmlfc's thread about Aqua-Glos and Flora-Glos. Take a look at each of the SPDs on these pages...

Flora-Glo Spectral Distribution:

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+8066+12766&pcatid=12766

Aqua-Glo:

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+8066+12763&pcatid=12763

It looks as though the Flora-Glo, although advertised as 2800K, should be assigned a higher K-rating, and that the Aqua-Glo, given an 18,000K rating, has quite a bit of red in it as well as blue. The Aqua-Glo actually looks like it should do better with plants, given the apparent spikes in some of the spectrums. Weird that the Flora-Glo is advertised as the plant bulb.

Just wanted to give an example of how K-rating can sometimes look as though it really has nothing to do with the actual spectrum of the bulb.  8)

[nacra99]

Re: 6700K, 10000K, Actinic...

So our main concern with corals is to get useable light to their photosynthetic algae? Does algae use a different spectrum of light than vascular plants?

Yes and no... ok warning.. science content..... Zooxanthellae are the cellular organisms (dinoflagellates) that live in coral, anemones etc. They are predominantly brown in color. Loosely.. their role is to photosynthesize food from light for themselves and when there is excess, the "leftovers" go to feed the host. The best lighting for photosynthesis is normal sunlight, which (very) loosely translate to full spectrum 5000K - 8000K, Which is the same as fw aquarium plants. However, since zooxanthellae are brown, a spectrum leaning towards sunlight will cause the coral to look very brown. Not pleasing to the eye at all.

Now i said "Full Spectrum" because there is no such thing as a 1 wavelength aquarium light. Remember that white light is made out of many components with different wavelengths known as a spectrum. All aquarium bulbs emit a range of wavelengths.. from red to blue. Some have more blue then red and vice versa. The proportion of blues and reds translates into a unified visual color which our eyes perceive as a single color (say white light), which we identify with a "K" rating. Which is why i say that (very very) Loosly, we can say that the "K" rating reflects the proportions of the components of the visible light. You can sometimes see a picture of these proportions of wavelengths on the side of bulb packing.

But corals and plants (unlike us) are able to "see" individual components. In the case of corals, they recognize and have a preference for a particular wavelength of red and a particular wavelength of blue in order to photosynthesize efficiently. Zooxanthellae enjoy peak "food production" when they get higher doses of a particular red spectrum and a particular blue spectrum (Moderately sharp blue and red peaks). Now you can provide enough blue and reds by just increasing the intensity of an ordinary bulb, but this means that it will increase all extraneous spectrum between the wavelength that the plant/coral actually needs. This causes visual and heat overload which may bleach coral and kill plants. Which is why many reefers use a combination of bulbs with different peaks of red (usually daylight) and blue(usually actinic) in order to meet the zooxanthellae's specific needs without the extraneous spectrum. So this is the "Yes" part of my answer to your question.

As for the "No".. we remember that corals fluoresce. This is important for visual impact. Reef guru Anthony Calvo thinks that fluorescence is the coral's way of reflecting "extra" wavelengths within the spectrum that it doesn't need. This happens to be the bluish wavelengths. (which is not surprising since seawater creates an abundance of blue under water). Incidentally this wavelength (about 420nm -ish) is emitted by actinic lighting. Which is another reason why actinic lighting is used in reef aquaria. Hence coral growth is not the only concern, visual impact is also important.

Most "green" plants require a broader range of red wavelengths than blue (i.e broad red peak and small blue peak) compared to corals to photosynthesize efficiently. They can get a sufficient amount of "blue" from most common fluorescent bulbs. Neither do they fluoresce. Hence they have no need for actinic lighting.

I think one of the hangups I have concerns the lighting as it applies to us. I really don't care how it looks, I would much rather have it be beneficial to the plants in my tanks. Like Walter said, it boils down to what you want as far as growth and what looks good to you - I don't care about what looks good to me.  :)  I'm just wondering what the plants need.

Ditto. FW plants will do well with any spectrum which simulates "daylight".

I know it's been discussed umpteen times everywhere, but there are so many different opinions, and I don't understand why opinions would matter, you know?

Not to mention bad and misleading information.

So, I think, well, at least, what I'm getting from your posts is that photosynthetic algae benefits from the blue-er end of the spectrum, and plants from both blue and red?

Not quite... see above.

I think where I got lost was in the assumption that Kelvin somehow reflects (oh, bad word for a lighting discussion, sorry) what the spectrum of the bulb is.

Not quite.... Kelvin rating reflects the perception of color (or more exactly a comparison with carbon at a particular temperature)  and it only loosely translates into the components in the spectrum. Remember that white light is made out of a spectrum with different wavelengths. Plants and coral are able to discern each wavelength better than we. Hence when choosing light for photosynthesis, i usually recommend choosing lighting with respect to spectrum rather than kelvin rating.

I'm still a bit confused, also, on what an actinic really is. Is it just a light with peaks in the blue spectrum? Is there a K value recommended for actinic? (I'm now remembering my first shopping trip to get lights for my new plants, and having to spread out all my options next to eachother so I could compare their spectrums...) For plants, you want peak in the red and blue, correct? Does that correspond at all with Kelvin?

True actinic peaks at around 420nm. I.e there's a lot more blue than red.
It's usage is mentioned in my tirade above.

Phew... that was a long one...  8O
I guess 3 credits of Geosci 420 - Coral Reefs actually paid off.

[nacra99]

Re: 6700K, 10000K, Actinic...

Just wanted to give an example of how K-rating can sometimes look as though it really has nothing to do with the actual spectrum of the bulb.  8)

Yes!!  Finally someone gets it. I have been trying to explain this to everyone for years!!  

We should look at wavelength peaks rather than K-rating when choosing lighting

[Mzungu]

Re: 6700K, 10000K, Actinic...

Well, my questions almost made it a whole year without a response!!

Thanks for the answers, nacra.  8)  It is safe to assume, though, that I had my nose in book after book and article (uhh, published article) after article about this stuff after posing my unanswered queries.  

What was really confusing me was all the erroneous assumptions out there. But I think I get the majority of it all now.

But seriously, thanks for the response! I left for the ALA Convention on Wednesday, and didn't see your posts until today.

[mahoro]

Re: 6700K, 10000K, Actinic...

on both of my planted tank, i use all 10k bulbs, my plants are all growing fine, anything from 5500 (6700 is the best, even tho it looks weird to the naked eye) to 10k will grow plants...