# The Best Kind Of Lighting For Plants



## chilob (Feb 16, 2010)

I Have A 80 Gallon Tank And I Have 50/50 Power Compact Lighting . Should I Go With 6700 Kor 10,000k Or 12,000k .what Is The Best For Plants And Fish Color


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## Newt (Apr 1, 2004)

Ahhhh, another SW lighted planted tank.

It is best to mix your kelvins so that you provide the best of the blue and red light needed for plant photosynthesis and to get a color light you like to view your tank with. Dont be afraid to go lower unless you like the looks of blueish light. You need to buy good bulbs so you dont get a lot of green light in the bulbs spectral output; like in coralife bulbs.

Most europeans are down around 4100K and top off at 6000K which is rare. The GE9325 would bring out colors in your fish but the CRI is low so you will need to balance it with a higher CRI and whiter light.

How many bulbs and wattage size does your fixture take?


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## chilob (Feb 16, 2010)

4 36 Watt Bulbs Should I Go With 65 Watt Bulbs


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## chilob (Feb 16, 2010)

4 36 Watt Bulbs


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## Newt (Apr 1, 2004)

:wink:


chilob said:


> 4 36 Watt Bulbs Should I Go With 65 Watt Bulbs


I dont know if your current ballast will drive 55/65 watt CFs.
Do you know what your ballast is?

Your lighting level is on the low side. 55 watters would be better with separate power cord for two banks.

Sorry about the SW reference. I always scratch my head when I read that planted tank keeper use SW lighting. I just dont understand where it come from. You dont see this in europe.


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## Philosophos (Mar 1, 2009)

Coralife and some others sell their CF lights with 50/50 actinic, it's also that some of the big box stores stock for bulbs.

Light is a question of aesthetic more than anything. 50/50 bulbs actually have decent plant growth spectrum, and anything between 4500 and 10,000K gets used and works. Higher would probably work too, but it might look rather blue.

K rating really doesn't determine PAR, and not everything that falls within PAR has the same PUR. People get themselves concerned with bulbs far too easily. Do what looks good first, and unless it's black lighting you can probably grow plants with it.


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## Newt (Apr 1, 2004)

Here's an actinic spectral graph, 460 nanometers:








Yes, lots of blue light but most of it misses the absorbtion area by FW plants.
as seen on this graph:









Here's a GE 5000K so called 'Full spectrum light':








>>>>>>and another by Philips............NOT he same pattern at all.









AND then you need to look at intensity (the energy in that spike) for the blue and red peaks that enable plants to carry out photosynthesis. You need a normalized spectral plot for that:

















Not all bulbs are made equal. Yes, a bulb between 3500K and 10,000K will make your plants grow but some will do a better job than others. If you want both good leaf growth (from blue light) and stem elongation (from red light), you need light in both the blue and red spectra for photosynthesis and green for you (brightness as perceived by humans).


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## Philosophos (Mar 1, 2009)

Light discussions are fun 

I'd like to start off with amending the PAR/PUR chart you've posted to compare quality against. I find this one a little more telling, but still incomplete:









Notice in the lower parts that growth doesn't just bottom out completely with efficiency, and that carotenoids increase the usable spectrum by a nice little bit. Anthocyanins aren't even on this graph, but some such as phycoetherin are actually targeted for the 550nm range:









On the topic of PUR, not all plants have the same ratio of chlorophylls and carotenoids, and in-situ measurements are impossible. For all the lights I've tried, I find that light distribution, CO2, flow and nitrogen have far more to do with color or internodal spacing or leaf growth than the quality of light being used.

Now if that isn't enough, plants also go through chromatic adaptation. This means they have a dynamic PUR, and depending on what's available around them their optimal color range will actually change.

When examining those spikes, you'll notice some reliable expenditures at the ~435, ~550, ~650nm points. This means there's a large expenditure in the same places, two of which are optimal for typical plant growth.

As for actinic; I would not advise using pure actinic. The Coralife 50/50 is interesting though:









All of this is why I find that the aesthetic value of the light should be considered above all else.


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## Newt (Apr 1, 2004)

Here is a better graph showing carotenoids, phycoetherin, etc.









I didnt disagree that almost any bulb will grow plants. However, the thread was asking for the best kind of lighting for plants and that is not chosen by aesthetic value IMO.

That coralife 50/50 graph looks just like their 6700K bulb:








Lots of green light makes for a green hue. I dont like this type of light and it is found in cheaper light bulbs.

As far as "expenditures at the ~435, ~550, ~650nm points" : The 550nm is green for the human perception of brightness which is where lumens comes from. Additionally, there are very few fluorescent bulbs that produce light (strong spikes) in the 650nm range as this true red phosphour is very expensive. You find it in Sylvania GroLux Std (strongest), GE Freshwater and the Perfecto (with possibly a few others). All others produce orange/red at 625nm. Blue regions tend to have one or two important peaks.
For green plants the lighting peaks that are most important:
Chlorophyll-a: 430nm/662nm 
Chlorophyll-b: 453nm/642nm 
Carotenoids: 449nm/475nm


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## Newt (Apr 1, 2004)

I asked the mods to move this thread to the Lighting section.


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## Philosophos (Mar 1, 2009)

Good call on the move.

Actually, the OP was wondering what the best one for plant and fish color is:


chilob said:


> what Is The Best For Plants And Fish Color


I submit that if someone is concerned with the aesthetic value of their tank, then meeting this requirement is much more important than yeild. No doubt every plant has some sort of hypothetical optimal light for efficiency, I just don't see it being so important as aesthetic.

I also can't say that I've seen much for morphology with different types of light that can't be controlled better in other ways.

You really can grow plants with almost any bulb, the question is whether it's worth your time and effort. Not all bulbs are optimal, not all are pleasing. If it looks amazing though, and it's worth your time, odds are you can grow a plant with it.


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