# The biology of the color "red"



## MiamiAG (Jan 13, 2004)

We come across questions about "How to get X plant red?" all the time. Most of the answers given are based on experience, what we've read on the net, or hearsay. What is it that will make Rotala macranda take on its beautiful red hue? How do we keep it red? 

I remember going with Claus Christensen of Tropica to visit Brad at Florida Aquatic Nursery. One of Claus' comments to me was that they couldn't get their macranda as red as Brad could. Why is that? Tropica is much more technologically advanced than FAN. Couldn't they reproduce the conditions?

Is it the pH, light intensity, iron content of the water, differences amongs the species, substrate nutrients? 

Please share your experiences.


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## Gomer (Feb 2, 2004)

well...for me, low N only brings out extreme shades of red, but you don't need to be deficient to get out some really nice reds with some plants. I find that high light and Iron levels are good.

Here is a poor quality picture (IMO) of some of my ludwigia glandulosa. NO3 is usually around 5-10 (try to maintain 10ppm). 29g tank with 2x 55 9325's.










I have however found that to get good reds out of rotala indica, that low NO3 levels are required. I can't get good reds out of of it in my 29g unless I drop N.

Also, if you look at my L. Repens pictures in the plant photography page...the RED repens was much lower light than the orange repens. The red one was also NOT under lights that bring out reds. The difference was nitrate levels. the deep reds were when the plant was kept with lower NO3 (5 or less).


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## Phil Edwards (Jan 22, 2004)

I visited Neil Frank a couple months ago and his plants are BRIGHT red as are Diana Walstad's, particularly their Rotala macrandra. What intrigues me is their general low Nitrate levels. Neil doesn't dose much but does have significant amounts of peat in his substrates and Diana don't dose at all, though the decomposition in her tanks puts off what her plants need. Both people can grow some very healthy plants under these conditions and they happen to be bright...

That got me thinking that perhaps in some tanks it's a symptom Nitrogen deficiency. Because the plants don't have as much food they don't produce as much Chlorophyll. Since Chlorophyll masks the other pigments the red coloration should come out more.

Although I haven't tested it yet, I feel red coloration also depends on the color spectrum of the light it recieves. Since the Carotenoid pigments are best at absorbing blue light, bulbs with a higher amount of blue output should encourage red pigmentation in the plants. I've received quite a bit of anecdotal evidence to corroborate this, but haven't done it yet myself.

Finally, light intensity. Most of us have had plants get redder the higher in the tank they are and/or as more light is shed into the tank. Some folks think this is a "sunblock" reaction. Without knowing the biochemistry behind it I'd have to disagree. If plants underwater need to protect themselves from the sun why aren't all land plants red? Wouldn't they want a blue pigment to reflect the harmful high blue/UV spectra? Furthermore, why are so many species of photosynthetic algae that live at depth red?

Here's some interesting information: 
The Solar Constant, the amount of incoming solar radiation (insolation), that reaches the upper atmosphere is equal to 1370 watts/square meter. The SC for the earth's surface is between 800 and 1000 watts/square meter, depending on altitude and atmospheric conditions. That's an average of 800 watts/32 square feet at sea level under average open sky! Take into account the effects of humidity, clouds, and possible cover from other foliage and you're talking less than that.

Consider the average high light aquarium with 3.0w/g (165watts) over an area of 4 square feet (55g). *Nature=100watts per 4 square feet, Aquarium=165 watts per 4 square feet, that's an increase of 65% over nature!!!*

Are those plants are growing so fast under that much light that they can't produce that much chlorophyll? I think the more likely reason is that there's so much light getting to them relative to their needs that they don't need to expend all that energy creating excesses of pigments they don't need much of.

Insolation and solar angle would also explain why FAN's plants are redder than Tropica's. The greater solar angle in Denmark decreases the amount of light available to the plants vs. the pretty direct light in Florida.

Best,
Phil


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## tsunami (Jan 24, 2004)

For me, the best way of getting reds was to lower NO3 *and* raise PO4. I generally keep nitrate at around 5-10 ppm in my aquariums, which didn't really bring out red coloration very well if at all. Raising my PO4 values to about 2 ppm increased and improved the coloration of my red plants immensely (especially Ludwigia arcuata). Not only that, the green plants are shimmering, emerald green and the Anubias nana leaves are finally free of spot algae!

I think red coloration is really not a factor of lighting. It's mostly dependent on your NO3 and PO4 levels. Of course, keeping your Fe and trace dosing high in those high light tanks is important, too. It's a combination of factors... low NO3, high PO4, lots of iron/traces.

Carlos


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## Justin Fournier (Jan 27, 2004)

Phil,

I think something might be lost in translation in reference to your conversions. Put 165W over a 55G and you still can't grow half the coral that grow in the ocean. Add 500W on that 55G and you can grow the corals one can find on the reef crest. 

Any ideas?


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## HeyPK (Jan 23, 2004)

Assuming 800 watts of incoming solar radiation per square meter at the earth's surface, I get 74 watts per square foot, assuming 10.76 square feet per square meter. 4 x 74 gives 297 watts of solar radiation over a 4 square foot area. 

Since flourescents are at best, 40% efficient, you would need 743 watts of flourescent lighting per 4 square feet to provide 297 watts of radiation.


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## Justin Fournier (Jan 27, 2004)

Good job HeyPK. That makes a lot more sence to me.

I saw the room Nasa did, replication full sunlight @ noon @ the equator or something to that effect. It was literally hundreds of lights. Way more then watts/32 square feet. But then again, Nasa isn't perfect :lol:


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## hubbahubbahehe (Mar 29, 2004)

Phil Edwards said:


> I visited Neil Frank a couple months ago and his plants are BRIGHT red as are Diana Walstad's, particularly their Rotala macrandra. What intrigues me is their general low Nitrate levels. Neil doesn't dose much but does have significant amounts of peat in his substrates and Diana don't dose at all, though the decomposition in her tanks puts off what her plants need. Both people can grow some very healthy plants under these conditions and they happen to be bright...
> 
> That got me thinking that perhaps in some tanks it's a symptom Nitrogen deficiency. Because the plants don't have as much food they don't produce as much Chlorophyll. Since Chlorophyll masks the other pigments the red coloration should come out more.
> 
> ...


Where did you get the info that 4 square feet in nature gets 100 watts?


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## Phil Edwards (Jan 22, 2004)

Check Paul's math, it's better than mine.


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## plantbrain (Jan 23, 2004)

Aquatic plants max out their staturation levels(adding more light will not increase biomass) at 500-600 micro moles/photons/m^2/sec.
Full Sun in FL is about 2000 micro moles/photon/m^2/sec.

Reef crest will take 1000W+ Halides sat over top the corals to coke even close to full sun.

Light compensations points dip down to 10-20 micromoles/photons/m^2/sec(Where Photosynthesis = Respiration)

I've seen some excellent color on many plants with 2w/gal of NO FL's.

There are some differences between species, methods and N stability(able to keep it at a low level) but a really red plant might be considered an unhealthy plant in a certain sense, N stressed.

Non CO2, low light allow for a lot of wiggle room stabilizing low residual NO3 levels. 

Regards, 
Tom Barr


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## DutchMuch (Apr 12, 2017)

Phil Edwards said:


> I visited Neil Frank a couple months ago and his plants are BRIGHT red as are Diana Walstad's, particularly their Rotala macrandra. What intrigues me is their general low Nitrate levels. Neil doesn't dose much but does have significant amounts of peat in his substrates and Diana don't dose at all, though the decomposition in her tanks puts off what her plants need. Both people can grow some very healthy plants under these conditions and they happen to be bright...
> 
> That got me thinking that perhaps in some tanks it's a symptom Nitrogen deficiency. Because the plants don't have as much food they don't produce as much Chlorophyll. Since Chlorophyll masks the other pigments the red coloration should come out more.
> 
> ...


i just got done reading this thread and phils post(s) stood out to me the most. 
I dose EI with the NilocG mixable dry fertz, so... i dose 10ml of micros And macros every other day (dif days for each, dont dose sunday) in my 40b... Should i increase dosing? or even triple this?


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## hoppycalif (Apr 7, 2005)

I think there are some bad assumptions in that post. For example, you cannot equate watts per gallon or watts of lighting to the solar constant, which is expressed in watts of sunlight. A watt of electricity powering a light bulb is far from being a watt of light. Since light bulb efficiency is expressed as lumens per watt, not watts of light per watt of electricity used, and lumens is not a measure of total light, but light as seen by humans, I don't know how many watts of electricity are needed to produce a watt of light. Even if I did, the light from a fluorescent bulb is so much different in spectrum than the light from the sun, I don't think there is a way to calculate the efficiency of a light bulb. But, lets just assume a typical bulb converts 10% of the electricity it uses to light energy. If that is close to being the case, the 165 watts per 4 square feet mentioned is really about 16 watts per 4 square feet, which is about 16% of sunlight, something I believe we all know anyway. (PAR from direct sunlight is roughly 2000, while typical aquarium lighting is 100)


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## DutchMuch (Apr 12, 2017)

wait so Should i increase dosing?


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## hoppycalif (Apr 7, 2005)

If you follow the EI tables you shouldn't be off too much on dosages. The tables assume high light, so you shouldn't need to dose more, except for very unusual situations. With less than high light you could reduce the dosages.


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## Yorkie (Sep 8, 2014)

Phil Edwards said:


> The Solar Constant, the amount of incoming solar radiation (insolation), that reaches the upper atmosphere is equal to 1370 watts/square meter. The SC for the earth's surface is between 800 and 1000 watts/square meter, depending on altitude and atmospheric conditions. That's an average of 800 watts/32 square feet at sea level under average open sky.


Hi Phil Edwards

Sorry, I'm new around here so it seems a bit impertinent to be picky. Therefore, please accept this is an observation, not a criticism: 1 square metre = 10.76 square feet.

Yorkie


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## Gerald (Mar 24, 2008)

Good point, and you were the first to notice (or at least comment) in 2 years! Another consideration is that 80 watts of light energy (solar radiation) is more light than what you'd get from an 80 watt (electrical use) light fixture, even for a pretty efficient one.


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