# Making LED fixture for demanding plants



## Bucha (May 22, 2016)

OK, I decided to design and make LED lighting for my tanks. I have two identical 40 gallons tanks, one stands in a room filled with daylight, another in a room with a single tiny window. They have identical compact fluorescent lighting, filters, similar fish and plants (quite demanding), identical water composition, CO2 and fertilizing, but the first tank flourishes, the second barely survives continuous algae problems. I am weekly measuring nitrates, phosphates, magnesium, calcium, potassium, sodium and chloride ions - they are the same and reasonable.

Yes, I did try a commercial LED fixture to no avail - some plants became white, some just died, algae flourished. I got very annoyed, bought a scientific spectrometer, measured the fixture's spectrum and found it unacceptable. Then I went to several aquatic stores, and measured spectra of many other LED fixtures, including $600+ ones (with store-owners consent, of course), and they were essentially all the same as for the one fixture I tried. I am intentionally omitting the brand names, this is not an advertising. But I am determined to make a LED fixture that works better. I need to do the research first, and will be posting my accumulating knowledge here, in hope that it may help someone else.

Aquatic plants use light for two purposes: Photosynthesis and Decision-making (when to germinate seeds, produce shoots, bloom etc.). The sun produces electromagnetic waves with wavelengths from about 290nm to 3,200nm. Plants use mostly the *400-700nm* part of the solar spectrum, which is called *PAR* (*Photosynthetically Active Radiation*).

The ratio of energy in the PAR region (400-700nm) to total solar radiation is around 0.5. It is nearly independent of atmospheric conditions.

During photosynthesis plants absorb CO2 (molecules consisting of one Carbon atom and two Oxygen atoms), use the carbon atoms to make their tissues (to grow) and release the remaining oxygen. However, plants also breathe, or burn their carbon reserves to obtain energy for various things they need to do. Breathing (respiration) consumes oxygen and releases CO2 back into the environment. A condition when amount of CO2 taken for photosynthesis is equal to the amount of CO2 released during respiration is called *Compensation Point*. If there is not enough light for the photosynthesis to be faster than the respiration, plants will use carbon from their tissues to breathe, they will inevitably run out of the carbon and will die. Low-light plants use the light more efficiently and their Compensation Point is low. Hight-light plants need a lot of PAR to achieve the Compensation Point.

On the other side, plants can not photosynthesize with indefinitely fast speed. If the amount of the light keeps increasing, the plant will try to grows faster. However, eventually, light intensity will increase up to the point when plant's photosynthetic machinery can not keep up. This is called *Saturation Point*. Having a fixture with light intensity above the Saturation Point is not only wasteful, it is very bad for plants growth.

Light is not a benign thing, it makes the life possible, but it always produces free radicals, which indiscriminately destroy various complex molecules used for photosynthesis and other life processes. So, while photosynthesizing, the plant also continuously repairs the light-induced damage. At lighting intensities above the Saturation Point the plant may become *Photoinhibited *and eventually die.

Not all *400-700nm* PAR is equally good for out tanks. We all want to grow more advanced (Vascular) plants, not the algae. Our plants mostly need blue (*400-500nm*) and red (*630-700nm*) light, because they harvest energy using mostly Chlorophylls A and B. However, Nature did not waste the remaining yellow and green energy, this light is often used by algae. For example, in many cyanobacteria the main light-harvesting pigments are two phycobilins, rather than chlorophylls, they use bands in *550-615nm* greenish-yellow-orange region.

Additionally, plants produce very important pigments called *Carotenoids*, they neutralize the photo-damage and need blue-to-cyan (*430-520nm*) light to function.

Also, I must make sure my fixture has wavelengths not only for photosynthesis, but for the plant's Decision-making (see above).

The task is complicated by the fact that not all wavelengths can be achieved using LEDs existing to date. Also, aquarium walls are transparent, this makes it possible for the light energy to be lost in the room. Also, I need to make sure there are no dark spots in the tank.

Therefore, I need to make research and decisions on:
1. Optimal light intensity
2. Optimal light spectrum
3. Technical issues

I am going to do the "Optimal light intensity" research first and will post it once I have something useful.


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## DutchMuch (Apr 12, 2017)

Following.


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## Maryland Guppy (Mar 5, 2015)

Bucha said:


> one stands in a room filled with daylight, another in a room with a single tiny window.
> but the first tank flourishes, the second barely survives continuous algae problems.
> 
> I got very annoyed, bought a scientific spectrometer, measured the fixture's spectrum and found it unacceptable.


The tank receiving daylight has the algae issues?

What meter did you buy?

How are you measuring PAR?

Optimal light intensity would be in regard to the plant species you wish to grow?


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## Bucha (May 22, 2016)

To Maryland Guppy:
Growing IS difficult, it does not depend 100% on you, my post is highlighting this! 
Nature is so very much more complex and interesting than you think. Arrogance is not appropriate here. 
1. No, the tank with daylight is flourishing, did you even read my post?
2. I purchased ASEQ Instruments, LRI-B (V1.0, 16 bits). This is a spectrometer for 190-1300nm range. It was calibrated at NIST in mequivalents/(m2*sec) - a scientifically accepted units for measuring RAR. 
3. I am RESEARCHING the optimal PAR for high-light demanding plants, once I am ready, I will post details for everyone to use.
Again: My hope and goal are to help myself and people here to grow beautiful plants, not to boast how easy it is for myself to grow.


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## Maryland Guppy (Mar 5, 2015)

Bucha said:


> To Maryland Guppy:
> Growing IS difficult, it does not depend 100% on you, my post is highlighting this!
> Nature is so very much more complex and interesting than you think. Arrogance is not appropriate here.
> 1. No, the tank with daylight is flourishing, did you even read my post?
> ...


Sorry you didn't like my signature.

1. Just verifying the sunlight theory. With so much wind in one's sails I had to validate the presented content.
2. Is this meter really worth the expense? Do you plan on marketing an LED fixture?
3. Many are already familiar with PAR ranges for many plant species, again what plants peak your interest?

There is an excellent plant finder on this site with detailed descriptions.
Many more on other sites too, to help in plant selection and suitability for one's tank.

Many sites still post in watts/gallon, by today's standard it doesn't help much.
Wish they all listed PAR ratings instead, but who is going to re-write it all?

Many are using commercially available LED fixtures and growing quite well.
Granted they are covering their tanks with more than 1 fixture.
T5HO is still very popular and many won't transition to LED due to excellent growth.
MH is still be used used in planted tanks.
All the more reason for a "PAR" preference for aquatic species.


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## Bucha (May 22, 2016)

No Marketing. The meter is an overkill for most people here. Also, the meter's software is awkward and unreliable, I am only able to use it because my spouse is a computer/electronics engineer. This is why I originally did not post the meter's brand name.

I am driven by curiosity here. I hope to accumulate info useful without buying anything at all.

I live in the area with several excellent aquatic stores. Their marine tanks are breathtaking, their freshwater tanks are depressing, and they all use "the best" LED fixtures available. I often see white plants with LED fixtures, while cyanobacteria is happy. This is NOT iron/nutrients deficienciy. I came to think it is from LED lighting (a very strong 460nm band not compensated by other wavelengths). I just want to get to the bottom of this. If I, indeed, succeed with the fixture, I may offer it for the display tanks in these aquatic stores. I am very far from the success yet.


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## hoppycalif (Apr 7, 2005)

None of us try to offend other people here. Some of us inadvertently offend others when jokes, subtle or otherwise, get taken too seriously. Please concentrate on what you have to offer, whether advice, experience, test results, etc., and ignore the extra words.

I will be watching the results of any tests like this with great interest!


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## DutchMuch (Apr 12, 2017)

^^^^^^


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## Maryland Guppy (Mar 5, 2015)

Bucha said:


> You signature indeed feels offensive.
> People come here to solve their problems, no need to patronize them.


Offensive it shall be. [smilie=b:

We all have "problem plants".
One cannot grow everything, it just won't happen.
My failures start with soft water plants, low KH & low pH.
Do I really want to change everything, maybe not.
There is enough species I can maintain very well with my existing water parameters.

Often try to help others solve their issues provided they give enough good information.

[URL="http://spectra.1023world.net/"]http://spectra.1023world.net/[/URL]
A useful LED tool that can be used for estimation.

PAR is one thing but if the PUR rating doesn't go over 70% I have my doubts.
Seneye has a Reef monitor that provides PAR and an estimated PUR rating in V2.0 firmware.
A useful tool for just under $200USD.

Don't discount the reef sites either.
There are some fine LED builders out there!
O2surplus & Theatrus on Reef Central.
They build many driver boards and LED puck arrays. Planted tank options too.


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## DutchMuch (Apr 12, 2017)

on behalf of my pal Marylandgoopy he is a member who has helped me many times over the years, his signature only spills truth. Also its a "blanket statement" so you cant just immediately assume hes talking about a specific plant or person etc.


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## Bucha (May 22, 2016)

Sorry guys! I did not mean to hurt anyone's feelings. I need your help and input and I love the site.


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## Bucha (May 22, 2016)

Optimal Light Intensity.

According to a 2006 paper in Limnology and Oceanography (Volume 51, N 6, 2006, pages 2722-2733), 15 mixes of various densities of the following aquatic plants were created:
Low light species: Vallisneria Americana "Natans", Vallisneria Americana "Gigantea", Sparganium Emersum;
Medium-low light species: Hygrophila corymbosa "Stricta", Sagitaria Platyphyla;
Medium light species: Sagitaria Subulata, Myriophyllum aquaticum, Egeria densa, Potamogeton Crispus, Potamogeton Pectinatus, several Callitriche sp.;
High light species: Cabomba caroliniana, Hygrophila corymbosa "Aroma"

Average *Compensation Point* was achieved at *119 μmol/(sec m2) of PAR*
*Beginning of Saturation* was achieved at *455 μmol/(sec m2) of PAR*
The actual Saturation Point was not achieved and is probably is 20% higher, at 546 μmol/(sec m2) of PAR.

A very good news is that we can approximately convert these values into W/m2 of light for out tanks simply by dividing them by 4.6, thus we receive:

Average *Compensation point - 26 W/m2 of PAR
Beginning of Saturation - 99 W/m2 of PAR 
*
We can do this because in 1972 K.J. McCree (Agric Meteorol, Volume 10, pages 443-453) published that *1 W/m2 (PAR) = 4.6 μmol/(sec m2) (PAR) for the Sun, metal halide bulbs, and fluorescent bulbs*.
While this was a long time ago, the same coefficients are still used in modern scientific literature. There were no commercial LEDs in 1972, but for white LEDs I think that the same 4.6 conversion coefficient may be assumed for now.

Now we can convert to W/gallons for our tanks. For example, my 40 gallons tank is 12 inches wide and 48 inches long, so the water top surface area is 12x48=576 square inches, which equals to 0.372 square meters (used Google to convert this). Therefore, for my tank with the same plants:

*Average Compensation point* - 26 W/m2 * 0.372 m2 = *10W of PAR*, or approximately *0.25 W/gallon of PAR*
*Beginning of Saturation* - 99 W/m2 * 0.372 m2 = *37W of PAR*, or approximately *0.92 W/gallon of PAR*

_But these are not Watts of electricity consumed by our light fixtures, but of light energy this fixture produces._

A light source transfers electric energy into light and heat. When buying a light source we need to look at its actual power (often presented in a small font), not the fashionable and large-font-ed power of an incandescent bulb producing the same amount of lumen. Then we need to find out how much of this power is actually transformed to light.

At https://www.dial.de/en/blog/article/efficiency-of-ledsthe-highest-luminous-efficacy-of-a-white-led/ there are theoretical maximum energy conversion efficiency for several light sources:
T5 fluorescent, 54W: 23.7%
Metal Halide, 70W: 31.5%
Warm white LED, 35W: 42.3%
Cool white LED, 16W: 48.7%

According to a 2009 paper in Nature (Volume 459, pages 312-314), fluorescent lighting transforms 10-15% of the input energy into light. According to Chapter 4 of a modern textbook "Energy and Fuels in Society" by Ljubisa R. Radovic from Penn State University, typical efficiency of a fluorescent lamp is 20%.

According to data-sheets of several LED manufacturers (Lumileds, LedEngine and Luminus) their LEDs transform 17 to 63% of inputted electrical energy into light. It is an awfully wide range! Once/if I come to the technical parts of this project, I will buy a few dozens of LEDs with appropriate PAR wavelengths from several manufacturers, measure their actual spectra and actual efficiency and will post it here.

Metal halide lamps imitate the Sunlight better than fluorescent and LEDs light sources (Wang W. Simulate a "Sun" for solar research: a literature review of solar simulator technology. Stockholm, Sweden; 2014). Unfortunately, efficiency of metal halide lamps depends on their power, those used for stadium lighting are highly efficient, but those for aquariums not so much.

Based on the above data, my best (and I believe pretty good) guess of *average efficiencies of modern aquarium fixtures and light bulbs are:
Fluorescent: 20%
Metal Halide: 25%
LED: 40%*

From here, can be found that to achieve the *10W (0.25 W/gallon) Compensation Point* (plants barely alive and not for long) in my 40 gallons tank I would need:
10W/0.2= *50W (electricity)* fixture if using *fluorescent lighting*
10W/0.25= *40W (electricity)* fixture if using *metal halide lighting*
10W/0.40= *25W (electricity)* fixture if using *LED lighting*

To achieve the *37W (0.92 W/gallon) beginning of Saturation* (plants happy) in my 40 gallons tank I would need:
37W/0.2= *185 W (electricity)* fixture if using *fluorescent lighting - 4.6 W/gallon (electricity)*
37W/0.25= *148 W (electricity)* fixture if using *metal halide lighting - 3.7 W/gallon (electricity)*
37W/0.40= *93 W (electricity)* fixture if using *LED lighting - 2.3 W/gallon (electricity)*

Most of the plants discussed in the publication's set-up have low and medium light requirements. I think that aquariums densely planted with light-hungry species will need *twice more light*, but it is just a guess.

I wish people here would post their light fixture type, electrical wattage, and list of plants that grow well at these conditions, then the actual practical values could be calculated and added to the Plant Finder.


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## DutchMuch (Apr 12, 2017)

ive got a 6 bulb 4ft agrobite T5HO with 6500k daylight bulbs (getting aquafloras l8tr on) substrate is 3 1/2" thick, high light plants only. Light is 12" exactly from rim of tank, tanks a standard 40b. I calculated once how many wpg i have but i forgot. think it was like 9.


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## hoppycalif (Apr 7, 2005)

Does that very interesting, long post discuss PAR at the water surface, at the substrate surface, or an average intensity in the tank? The PAR from any light source drops off with distance from the source. 

Our PAR meters all read in micromoles per square meter per second, so I think it is best to always refer to PAR using that scale. But, how do you decide on what level in the tank you should be measuring PAR and relating it to low light, medium light, etc.?


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## Maryland Guppy (Mar 5, 2015)

Bucha said:


> Optimal Light Intensity.
> 
> I wish people here would post their light fixture type, electrical wattage, and list of plants that grow well at these conditions, then the actual practical values could be calculated and added to the Plant Finder.


This would be a tall order.
Commercial lights have recorded PAR data points, if a manufacturer doesn't post their PAR data it seems bogus to me.
Someone would measure it and post their findings anyway.

For DIY builders all fixtures are different.
Wattage would not be relative to PAR data, different angle LED lenses affect this greatly.
Dimming capabilities can also alter light output.
Running an LED at reduced mA's can alter output too.
PWM dimming @ rated output offers the most constant display of light while allowing dimming capabilities.

Being a DIY LED type, I have settled on a puck design that is over all my tanks.
It requires dimming else there would be an algae farm!


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## Bucha (May 22, 2016)

Wow, thank you! It is becoming useful!

DutchMuch, according to Hydrofarm website (https://www.hydrofarm.com/p/FLT5464BK20) your light bulbs are 54W each. Also, according to the spectrum from their web page, all the light is produced in PAR region. Have I found the correct bulbs? A am sorry for asking a stupid question, but does "standard 40b" mean 40 gallons? (I immigrated to US and English is not my mother-tong)

If yes, then the calculations work and you seems to have perfect light for your high-light plants!

For DutchMuch tank with light-demanding plants:
54*6=324W of Electricity, which for his 40 gallons tank means 8.1 W/gallon Electricity
324*0.2=65W of Light, which for his 40 gallons tank with fluorescent lighting means 1.6 W/gallon Light (PAR)
65*4.6 = 299 μmol/sec of light, which for his 40 gallons tank means 7.5 μmol/(sec gallon) of Light (PAR)

If his 40 gallon is like mine 40g, with approximately 0.372 square meters of the water surface, he has
299 μmol/sec : 0.372 m2 = *804 μmol/(sec m2) (PAR)*

The paper in Limnology and Oceanography (described above) found that for their, mostly low to medium light plant collections, the Beginning of Saturation happened at *455 μmol/(sec m2) of PAR*, your practical value is almost twice higher, which makes perfect sense!

Hoppycalif: This post is so far about the PAR at the water surface per a square meter of this surface and it assumed that essentially all light energy produces by a bulb is directed into the aquarium. We need to start from somewhere.

I have not done proper research yet, but I strongly suspect that the distance to the water surface, substrate height and aquarium depth are all so very important, because we need to direct all the light into the tank and to KEEP it there. In reality, the light is emitted in all directions and is continuously absorbed, reflected and refracted from the fixture, plants, water and aquarium walls surfaces. I think that the energy of a direct light ray absorbed by the air and water column between the air and substrate (tank height) is much less then the energy continuously absorbed and reflected by plants, walls and fixtures. I will do the research and know more, at the moment I am not able to better answer your questions. But I want to find out about optimal spectral wavelengths first (just very curious about it), and only then will go into technical details.

My reading of scientific literature has been very frustrating, because (unlike the authors of the described paper) most people just take pieces of leaves, illuminate them directly in the tank and present ridiculously low PAR values for this particular plant, because it is grown ALONE in direct light. Their goal is to publish and receive grant money. Our goal is to grow beauty, we have tanks filled with a variety plants, ALL those plants absorb something and shade each other. So, here I am trying to find a way to calculate practical values ON THE SURFACE of a REAL planted aquariums for everyone to use, and from DutchMuch data it seems that we will be able to do it!

You see, there are often people here asking what lighting they should get for their new tank. They may be not ready to invest in a PAR meter. All they know are their tank dimensions and electrical wattage of the fixtures they think of buying. Simple arithmetic calculations here may give them a way to find out for themselves, depending on the lighting type they want and the plants they want to grow.

If DutchMuch lists the plants that are reliably happy, and if people working on the Plant Finder will be willing to participate, they may already be able to put the optimal PRACTICAL values for a PLANTED TANK for DutchMuch's plants in W/gallons of electricity and W/gallon of PAR (for the beginners), and in μmol/(sec m2) (PAR) for crazy people like us.

I wish more people posted their data here for the same or different plants...

I am very grateful for the Plant Finder existence, use it a lot, but at the moment it says: "A. gracilis is a moderately demanding plant which will not show its full potential unless its requirements are met. Lighting should be moderate to intense (2-3wpg or more)..." We need to know 2-3 W/gallon of what?

MarylandGuppy: I am truly very sorry for being rude to you. My tap water is GH2 and acidic, so, naturally, I try to grow hight-light plants. I am suffering with the "dark room" tank for several years, changed substrates, fertilization, fish, plants to no success. I live in a desert, adding huge excesses of nutrients and freuent water changes are not an option. I felt very stupid when read that growing is easy. Initially, I did not even realize that it was a blanked signature statement, I thought it directed at myself. I did not understand that you statement is meant to encourage other people to grow. Also, I understand that you are protective of the forum and had the perfect right to ask if I (a newcomer) am driven by commercial interests, but I felt hurt.

Please, forgive me! You are an expert, with your help and data we may be able to find optimal light values for the plants types you grow.

Wow, I have just noticed your answered! Thank you. I think the text above addresses some of your concerns.


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## hoppycalif (Apr 7, 2005)

Just to "brain storm" a bit: We really need to figure out a way to characterize lighting as high, low, etc., taking into consideration that light from any kind of fixture drops in intensity with distance. For typical fluorescent lights it drops approximately proportional to one over the square of the distance from the bulb/reflector. For typical long LED light fixtures, with lots of LEDs strung out in rows, and with typical 120 degree optics from the clear plastic protective "cap" over the junctions, the drop in intensity is closer to being proportional to one over the distance (not squared). This means a 20 gallon tank with the light fixture sitting on top of the tank, has a much lower light intensity at the substrate surface for a 20 gallon tall tank vs a 20 gallon long tank for the same fixture. I think the ideal light fixture is suspended about as far above the top of the tank as the tank is tall. That reduces the variation in intensity in the tank. All of this makes it very hard to say that an X wattage light gives you Y intensity for a 20 gallon tank. When I went through a less complicated study of this I decided I would have to use the intensity at the substrate level as the parameter for determining what is high vs. low light intensity. I have been hoping for several years now that someone like you would do some more serious thinking about this subject, than I was able to do.

I try to avoid sending people to other forums, but this is as far as I was able to go on this subject: http://www.plantedtank.net/forums/10-lighting/184368-lighting-aquarium-par-instead-watts.html


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## Bucha (May 22, 2016)

MarylandGuppy: Yes, this is a very a tall order. But if we manage to get people here to participate with practical data, it is possible to find out what PAR values are optimal for different plants set-ups. Then people will be able to better use manufacturer's PAR data, people here would have a better idea about the PAR they actually need.

Wattage is relative to PAR data, but agreed, we must take into consideration the angle of LED lenses. I bought 45 degrees lenses, have not received them yet. I will test them and post the results and drawings, if I can only figure our how to post the drawings .

Agreed that the dimming capabilities will alter light output. At the moment I am thinking of making 200W fixture with dimming, set it over the tank and experiment with outputs, then post here tank photos and PAR data (PAR and spectra)

Thank you for the rest of the advice! I will use it!


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## Bucha (May 22, 2016)

Hoppy: thank you! Wonderful post! We will do it together! Please give me time to carefully read it, think about it, so I could try to give an intelligent input. Work tomorrow...


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## Maryland Guppy (Mar 5, 2015)

Bucha said:


> Wow, thank you! It is becoming useful!
> 
> MarylandGuppy: I am truly very sorry for being rude to you. My tap water is GH2 and acidic, so, naturally, I try to grow hight-light plants.
> 
> ...


No one can be rude to me, I'm over fifty and grey!

Commercial interests, hurt? Come on now.
It's not even being protective even.
Every once in a while someone "feels" the forums for lighting ideas.
They talk big like they will build an ideal light fixture and sell it to everyone.
After 6 posts or so they are never seen again.

No expert either, far from it.
Still don't have a Dutch tank setup because I'm still playing with so many plant species.

Regarding ideal PAR for a species.
This is tough the way we plant in a tank.
Say we have 100 PAR (at substrate, typically measured here) and 15 species of plants.
They are all performing well, it is hard to say which ones would be sustainable in lower PAR.
Where would you put them to test a lower PAR level? Another tank? How many tanks?
Dim the entire tank some and risk some species suffering?
Many people would need to report their findings and have PAR meter accessibility.


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## hoppycalif (Apr 7, 2005)

Lighting was so simple when everyone used T8 or T5 fluorescent bulbs. All you had to account for then was the reflector quality. Now we have LED lights with hundreds of different things that affect how much light we get. I thought I could simplify lighting when I started working on it, but then LEDs came along and I gave up. Screw-in fluorescent bulbs are another variation that is very hard to simplify.

Before we can get much use from data reported by all of us we need to agree on how we measure the PAR that we say we have on our tanks. It is relatively easy to just use the PAR measured at the substrate, but that can distort our data sometimes. But, if we measure PAR at each plant, say near the middle of the plant, we get so much data it is even harder to make much sense of it. Then, there is the fact that those of us who used Apogee PAR meters got incorrect measurements because Apogee didn't realize that they needed a big correction to their in-water readings until a few years ago. (The readings were all about 15% low.)


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## Bucha (May 22, 2016)

Here are the meager finding of my literature search:

Freshwater Biology (2015) Volume 60, Pages 929-943 
_Elodea Canadensis, Egeria Densa, Hydrilla Verticillata and Ceratophyllum Demersum_ were grown for 3 years under 100 μmol/(sec m2) at the water surface. Relative growth rate (dry mass increase per a day) increases 2-4 times with light increase to 150 μmol/(sec m2) at the water surface.

New Zealand Journal of Marine and Freshwater Research (1994), Volume 28, Pages 235-241
_Lagarosiphon Major_ and _Myriophyllum Triphyllum_ were grown under 200 μmol/(sec m2) presumably at the water surface (authors did not specify this) for 14 hours of light per day.

Aquatic Botany (2015) Volume 120, Part B, Pages 205-211
_Egeria Densa, Hydrilla Verticillata, Lagarosiphon Major_ and _Myriophyllum Triphyllum_ were successfully grown for 2 months under both of 172 μmol/(sec m2) and 69 μmol/(sec m2) average light intensities measured at 5cm below the water surface. Average daily irradiance was 6.97 mol/m2 and 2.79 mol/m2 respectively which corresponds to 11.2 hours of light per day.

Aquatic Botany (2013) Volume 110, Pages 31-37
For _Myriophyllum Aquaticum_ light saturation occurs at 270-300 μmol/(sec m2). The plant was successfully grown for 3 months at both 280 μmol/(sec m2) and 85 μmol/(sec m2) adjusted 1cm above the water surface, with 16:8 h day/night cycle. The high-light growth was a little faster only with CO2 addition.

Plant Physiology (1976) Volume 58, Pages 761-768
Photosynthesis of _Hydrilla Verticillata, Myriophyllum Spicatum, Ceratophyllum Demersum,_ and _Cabomba Caroliniana_ was studied by immersing apical portion of the plants in a glass test tube and irradiating the tube with incandescent lamps, so, presumably, the given PAR values are measured at the tube's surface.
Hydrilla - Myriophyllum - Ceratophyllum - Cabomba 
Compensation point, μmol/(sec m2): 15 - 35 - 35 - 55
Saturation point, μmol/(sec m2): 600 - 600 - 700 - 700
Irradiance required for 50% photosynthetic rate, μmol/(sec m2): 80 - 120 - 145 - 160

I can not open Plant Finder anymore. The message is:
Access denied for user 'aquaticplant'@'10.%' to database 'aquaticplantcentral_com_pf'
Is something wrong?


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## Maryland Guppy (Mar 5, 2015)

Cannot open plant finder on my phone but have not tried PC yet.


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## Bucha (May 22, 2016)

I did not give up! I just got distracted with algae. It seems that by the choice of LEDs wavelengths it is possible to discourage Blue-Green algae, BBA and other red algae, some Green Spot... all those that use not only chlorophylls A and B for photosynthesis. But I got stuck looking for scientific names for common algae. I have access to scientific literature about LEDs and Algae, but all publications use scientific names only. So I created an algae list and have just posted it on the algae forum. Will you please look at this list and see if my descriptions correctly correspond to common names? Maryland Guppy?


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## Maryland Guppy (Mar 5, 2015)

I looked over the list and it seems solid.


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## roby70 (Apr 13, 2018)

If it can be useful here the measured pars of different commercial LEDs are shown
https://www.ukaps.org/forum/threads...ihiros-led-par-data-the-power-of-light.43178/
(please remove the link if it's to possible to insert it)

But I have a question regarding the calculation of necessary Watt/gal of some post ago. With LED I usually consider lumen instead of watt; an inefficient LED usually has a ration lumen/watt of 70/80, an efficient one more then 120/130.
If I consider a normal LED with a lm/W ratio of 100 I will have with your formula a saturation point of about 230 lm/gal.
But normally a good LED light is between 150 and 230 lm/gal.
With watt the calculation seems correct (more then 3 W/gal for saturation point), using lumen it seems not correct.
Is there anything wrong with my reasoning?


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## Gerald (Mar 24, 2008)

Question about PAR meters: Do they all measure the TOTAL light energy from 400 to 700 nm, or do some have the option of measuring energy in smaller intervals, such as 400-450, 450-500, 550-600, etc? If they only measure the full range 400-700 total, then 2 lights of very different quality could have the same PAR reading, for example a "good" plant light with strong red and blue peaks, versus a "bad" plant light with mostly yellow-green (500-600 nm) and insufficient red & blue. I'm sure this questions has been answered elsewhere, probably many times, but please forgive my lack of patience for seeking it out. Gerald


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## mistergreen (Mar 3, 2007)

Gerald said:


> Question about PAR meters: Do they all measure the TOTAL light energy from 400 to 700 nm, or do some have the option of measuring energy in smaller intervals, such as 400-450, 450-500, 550-600, etc? If they only measure the full range 400-700 total, then 2 lights of very different quality could have the same PAR reading, for example a "good" plant light with strong red and blue peaks, versus a "bad" plant light with mostly yellow-green (500-600 nm) and insufficient red & blue. I'm sure this questions has been answered elsewhere, probably many times, but please forgive my lack of patience for seeking it out. Gerald


PAR meters has one photo sensor that measures to the range of 400-700. You would need multiple photo sensors in one to parse the spectrum. You're right, it would treat yellow-green and blue-red similarly in readout.

I think plants do need small amounts of yellow-green to photosynthesize optimally though.


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## hoppycalif (Apr 7, 2005)

The best PAR meters give equal weight to every section of the spectrum between 400 and 700 nm. The good enough PAR meters give close to equal weight to most of the sections of the spectrum between 400 and 700 nm. Most of the PAR meters we hobbyists have fit into the second group. But, some of the PAR meters in use virtually ignore the spectrum above 550 nm or so. No PAR meter is made to provide a record of the spectrum being measured. That requires a different meter.


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## mistergreen (Mar 3, 2007)

A spectrophotometer could parse out the different spectrum. I think there's a DIY spectrophotometer out there.


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## Gerald (Mar 24, 2008)

Based on what you guys are saying, a PAR meter isn't sensing anything beyond what my eyeballs can do? 400 to 700 nm is the same range as visible light. Sure, a meter can assign a number in whatever units I want, which my eyeballs can't, but I can easily tell which of two lights looks brighter. A camera light meter would accomplish the same task. Am I missing something "special" about PAR meters?

EDIT: OK, I found a bit more info: our eyes respond best to the middle of the visible spectrum (yellow-green, 500 to 600 nm) and under-estimate reds and blues, whereas a good PAR meter is equally responsive to the full range.


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## mistergreen (Mar 3, 2007)

yup, that's the difference between a light meter and a PAR meter.


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## Bucha (May 22, 2016)

roby70: 

Sensitivity of human eyes is maximum at 555 nm (in the green region), which is one of the worst wavelengths to grow plants. Lumen measuring is predominantly concerned with yellow/green regions of PAR.

Sensitivity of plants is maximum at 660nm (quite far in red), which humans can barely see. Optimal for plants seems to be 80% 660nm + 20% blue. This makes it possible to make a white LED light for aquarium, because you can have a lot of red for plants, but for the lighting to appear white to you, very little green needs to be added. I will be posting a lot of details, but the bottom-line answer for your question: you should never use Lumen to assess aquarium lighting.


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## Gerald (Mar 24, 2008)

Thanks Bucha; looking forward to your additional details. "but the bottom-line answer for your question: you should never use Lumen to assess aquarium lighting." Yes, I realize a PAR measurement is a little better than a visible light measurement (Lumens), but if a PAR meter can't distinguish the important red & blue wavelengths from the less-useful yellow & green ones (all wavelengths 400 to 700 are lumped together) then the meter will still measure high PAR on a low-quality light (for plants) that's mostly yellow-green, correct?


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## roby70 (Apr 13, 2018)

I know the best thing would be to know PAR and spectrum but in different case we do not have them. If we use standard LED we have an idea of the spectrum but we do not know PAR. So to undestarnd if a light is enaugh we have only watt or lumen.. it's not the good thing but probably the best that we have.

If someone have better method .... thanks for sharing them


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## mistergreen (Mar 3, 2007)

I accidentally found this.

white LED vs Red/Blue LED for plant growth.


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## hoppycalif (Apr 7, 2005)

Human eyes are a very poor light meter. When we see a small difference in intensity, it is really a big difference. Our brain tries to adjust brightness so it looks "correct", so we can never trust it to show us what the actual brightness is. And, of course we are almost blind to red light, which is the dominant "color" in sunlight.

A couple of days ago I did some experimenting with my new LED light/dimmer combination. It reduces the intensity in steps, one step per click. I watched the light intensity my eyes saw vs what the PAR meter said. I could see the drop in intensity each time, but a couple of seconds later it looked just like it was before I clicked the dimmer. Only after I dropped the intensity in half could I clearly see a difference in the visible intensity. The next day I was curious about whether or not the dimmer would maintain the dimming after it was shut down overnight. When the lights came on I wasn't sure if it maintained it or not, until I used the PAR meter to verify that it did maintain the dimming. Our brains just aren't wired to make our eyes act as a light meter.


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## Marko_Sp (May 30, 2010)

hoppycalif said:


> I will be watching the results of any tests like this with great interest!


I will be wathcing too!
I have just finished my light and am very happy with results. But still have doubts. Only plant with problem is my Alternathera, which I have 8 years in same aquarium (old one, same ground, same fishs, same plants), and it was always most red in town, never problem... But the problem did not start with LEDs, but with neglecting aquarium care when I looked only on spectra aplication, which PSU, which optics, and such things. My CFL probably had lost their power, there was lack of CO2, I have not trim plants on time so Alternathera went to top, did not change water for weeks. And GDA come. Mostly affected are my red plants - Althernatera and M. Tuberculatum. I do not think that I will kill GDA just with light! Well, maybe with UV...

I have not PAR meter, I just see that all plants like LED light. Strong pearling, good coloration, except Althernatera.

You are much talking about PAR, right spectar and such things. But I believe that imitation of sun is best spectar. And this is changing during time of day, year, location etc. Too much things about how plants uses light is still unrecognized.

Our aquarium is for our eyes, so how to reconcile high PAR with high CRI, without promoting algae?


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## Gerald (Mar 24, 2008)

In this video, growing lettuce, the white LED with lower PAR gave 37% more growth (by weight) than the red-blue LED with higher PAR. (Red-blue also produced more bitter taste; might be an advantage if you're keeping plant-eating fish!)



mistergreen said:


> I accidentally found this.
> white LED vs Red/Blue LED for plant growth.


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## mistergreen (Mar 3, 2007)

Gerald said:


> In this video, growing lettuce, the white LED with lower PAR gave 37% more growth (by weight) than the red-blue LED with higher PAR. (Red-blue also produced more bitter taste; might be an advantage if you're keeping plant-eating fish!)


Or turn people away from eating greens.


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## Michael (Jul 20, 2010)

Welcome to APC!

This thread is pretty old (2018). Hoppy did a great thread on his DIY LED. Also, the availability of good LED fixtures is much better now so not many people build their own. If you have another question, it would be best to start a new thread.


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## jenefree (Feb 26, 2021)

Rasron said:


> So, did anyone in here actually tried to set up a LED lighting for your plants?! I am really interested to do this, however I am not really sure how, and if it would be really efficient.


Dude, this is a really old thread


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