# Colour temperature



## Dominic (3 Feb 2014)

How much does the colour temperature and kelvin ratings actually matter? I've heard someone say that it does not matter and depended more on the WPG? 

Is this true?


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## pepedopolous (3 Feb 2014)

The colour temperature doesn't matter but most lights for planted aquariums are between 6500-8000 kelvin. Plants look good under these lights, above 8000k is too blue.

WPG doesn't work. You need to search these forums for the topic of PAR. However, people often seem to have problems due to too much light NOT too little. If you don't use CO2 you need even less light.

P


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## Dominic (4 Feb 2014)

What happens if the lights are over 8000k? Or is that purely personal preferences?


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## sanj (4 Feb 2014)

Personal preference more than anything else.


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## Puntius (4 Feb 2014)

You can use 10000k tubes just dont use anything over 10000k tubes, a combination of 8000k and 10000k tubes are very nice.


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## KeyboardWarrior (4 Feb 2014)

I like 10K nice and crisp


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## JohnKoncz (4 Feb 2014)

the most natural look of the plants is made under the 6500 K bulbs (I think)


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## Alastair (4 Feb 2014)

I dont agree that WPG doesnt work. Its a guideline to help us know what range of lighting we have on our tanks ie low medium high etc. 
Par agreed is ideal to know but not everbody has the option of easily getting par figures or even a par meter.


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## Dominic (5 Feb 2014)

So even if you used a blue 'moonlight' light, this would still be enough for plants? As i've read its very encouraging to algae?


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## ceg4048 (5 Feb 2014)

You have to measure the PAR. That is the only parameter of light that plants care about. Whatever light it is, it must have more than the minimum PAR value in order to grow plants.

Algae also do not care about colors.

Cheers,


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## Sacha (5 Feb 2014)

So Kelvin doesn't matter. Does LUX not matter either?


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## Dominic (5 Feb 2014)

So what is the ideal PAR? Can you find the PAR value on many light bulbs? Or do you guys not look at the PAR much?


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## Sacha (5 Feb 2014)

You need something like a Seneye Reef sensor to measure PAR.


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## flygja (6 Feb 2014)

Kelvin doesn't matter to plants, but matters to you. Too warm and your plants won't look green enough. Too cool and everything looks dull.


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## clonitza (6 Feb 2014)

Actually I don't know if kelvin numbers are accurate, I mean I had one 965 and one 865 at home, both 6500k of course and the 965 was on the orange side without much on the greens and everything looked meh, poo like. I put it in the bin and now I'm using only 865s. Back to the OPs question, using normal bulbs (not black light and such), temp color matters only to the eye, you'll spend a couple of quids until you find the color you like. Anyway I found out that the old standard lids with T8s were perfect for aquariums, enough light to grow any plant but not too much to make it an algae saga .. but now with all the T5s, LEDs etc .. it's another story .. they figured out how to make more money. 

Cheers,
Mike


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## James O (6 Feb 2014)

ceg4048 said:


> Whatever light it is, it must have more than the minimum PAR value in order to grow plants.



ceg4048, Is the minimum PAR value a static figure or dependant on tank depth, distance from substrate etc?  Any further reading or schooling would be appreciated


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## ceg4048 (6 Feb 2014)

Hi James,
Yes, it is a static figure, but it is a different figure for each plant. The minimum amount of light necessary for survival is a value called The Light Compensation Point (LCP). More info in the following threads:
LED Lighting | Page 2 | UK Aquatic Plant Society
Do t8 lights really degrade over time? | UK Aquatic Plant Society
Please look - good for plants ? | UK Aquatic Plant Society
Cheap ASDA Ikea etc light bulbs | UK Aquatic Plant Society
Cheers,


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## James O (6 Feb 2014)

Thanks ceg4048! Great reading.  Extremely informative. 

Is there a list somewhere of plants and their preferred PAR range?


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## ceg4048 (7 Feb 2014)

No, I don't have any list. It's not really necessary and it really wouldn't help. There is no such thing as preference outside the context of CO2/flow/distribution. There are plenty of websites, including suppliers, who list "PAR requirement" such as high light, low light and so forth. Those are all illusions. PAR by itself does not determine plant health. A plant can be healthy and slow growing under a low PAR, or it can be unhealthy and fast growing under high PAR. People need to stop equating growth rate with plant health because that's where their troubles begin. Health and growth rate are two separate entities. Under a low PAR all plants grow slowly, under high PAR they grow quickly, under middling PAR they grow at a middling rate. There is no "preference" in this sense.

The best that can be said is that there are some plants with a low LCP. These are known slow growers such as Anubias, Crypts, Ferns and Mosses. These plants can survive at PAR levels down around 10 micromoles and below. This is a very low value and growth will be also very slow. But also they have a very low CO2 Compensation point so this means they do well in non injected tanks. Other plants such as stems have a higher LCP, perhaps in the 20-30 micromole region and these plants also have a higher CO2 Compensation Point, which means they don't do well without CO2 enrichment. These are the two extremes and of course, there are plenty of plants in the middle of that range.

20 micromoles is nothing. Below 10 micromoles you can barely even see inside the tank, so this tells you right away that people use way more light than they need to. Naturally, growth will be painfully slow at these lower extremes, so it's very easy to use higher PAR values to increase growth rates. This is entirely reasonable but one has to pay attention to the CO2 in order to support a higher growth rate, because CO2 grows plants, not light.

Cheers,


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## James O (7 Feb 2014)

Okay so basically plants will grow on as best they can regardless.

 The level of that growth being dependant on light, CO2 and ferts, any of which can become the limiting factor.(does light have the distinction of being the one of the three that can be overdone to damaging levels within normal ranges of the other two?) From reading your other posts:  lighting issues are 'usually'  too much light (when compared to current CO2 input & distribution)Looking at EI dosing is designed give more than required as uptake is then not limited by availability.  CO2 can be pushed sky high as long as you don't nuke your fish.  But all 3 parameters must be in some equirilibrium.

Reminds me of the photographic trinity: ISO - f/stop - shutter speed.  Well except that is was simpler


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## TOO (7 Feb 2014)

This article explains the relationship well (it is probably mentioned in some of Clive's links above). I think the ideal combination is the one with high co2 and low/moderate light (obviously both categories are flexible). As you can see in the diagrams this does not get you fast growth, but it gets you moderate and, most importantly, healthy growth with reduced chances of algae. High light-high co2 can also work of course, but the other option is probably the most viable for non-pros, i.e. more manageable.  

Tropica Aquarium Plants - Rådgivning - Tekniske artikler - Vandplanters biologi - Interaktioner mellem lys og CO2

Thomas


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## ceg4048 (7 Feb 2014)

James O said:


> Okay so basically plants will grow on as best they can regardless.
> 
> The level of that growth being dependant on light, CO2 and ferts, any of which can become the limiting factor.(does light have the distinction of being the one of the three that can be overdone to damaging levels within normal ranges of the other two?) From reading your other posts: lighting issues are 'usually' too much light (when compared to current CO2 input & distribution)Looking at EI dosing is designed give more than required as uptake is then not limited by availability. CO2 can be pushed sky high as long as you don't nuke your fish. But all 3 parameters must be in some equirilibrium.
> 
> Reminds me of the photographic trinity: ISO - f/stop - shutter speed. Well except that is was simpler


Yep, ISO f/stop shutter is a lot easier because they are all well defined, controllable and exact parameters. We are simply not in control of all the thousands of direct and indirect parameters associated with growth and health. We lack control of even the Light/CO2/Nutrients when you think about it. The light is not the same on every leaf on the same plant. Neither is the flow, gas diffusion rate or nutrient availability.

The same plant, under any given set of tank conditions can actually be low light and high light at the same time. The leaves at the top receive a much higher PAR than those at the bottom, which get shaded, so they behave as low light plants do and their growth is much slower.

Cheers,


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## James O (7 Feb 2014)

Well at least nature can cope with our bumbling 

Thanks for your help ceg, I've got plenty to mull over now


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## Dominic (8 Feb 2014)

Just wanted to say, great read ceg  Thanks


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