Lighting spectrum

[Beetlebug515]

Can someone shed some "light" on this subject? 6500K, 10000K, actinic, etc? I ask because I have been doing some shifting around in my tanks over the last few months experimenting with different lighting. What is best for growing plants? Are there really lights that are better at growing algae than plants based on the spectrum alone? My Finnex Ray 2 led light seems to be an algae machine, even on an 80X24X30 tank.

 

[Fat Homer]

When it comes to planted tanks there are a whole host of contributing factors that cause algae, although Lighting Spectrum is possibly one of the main ones, the length of time the bulbs are on also make a huge difference...

But honestly, you should probably read this Stickied Thread First, since it should answer most your questions regarding lighting a planted tank: http://www.monsterfishkeepers.com/forums/threads/lighting-a-planted-tank.73446/

 

[Beetlebug515]

That actually answers zero of my questions. I have read through that before, and while it is a good primer for tank lightning, it really only addresses lighting intensity all of which can be boiled down to PAR values. I am trying to understand how the lighting spectrum affects the tank. Are low spectrum red lights actually more beneficial than white light alone? Assuming all values are equal with the exception of spectrum, do different light make a difference on actual growth?

 

[Pomatomus]

tl;dr warning. Feel free to correct me on anything if I'm wrong.

PAR is also related to spectrum, and spectrum is related to color temperature. PAR (photosynthetically active radiation) is the amount of light that can be used for photosynthesis (the useful part of light). This is not only affected by intensity, but also the color of light and the color of the plant. For instance, most plants appear green, meaning that they reflect the green light back at you and absorb the other colors (to keep it simple). You would have a tough time growing a plant in green light because very little of it will be used by the chlorophyll in photosynthesis. A red plant however, will be more able to utilize green light.

The spectrum of a given light refers to the different amounts of different colors in the light. Many bulbs (especially fluorescents) will show a graph with different colors showing peaks and valleys at certain colors. These refer to the relative amounts of each color in the light. If you're growing corals you tend to want more blue light (depending on natural depth) because red light is the first color to disappear as you go deeper in water (blue is last, which is why the ocean looks blue). Most corals experience blue light in the wild, and many can live in only blue light. Red is almost useless for most corals. Freshwater environments are often more shallow, so red is more prevalent in these environments. This is why many plants can utilize red light as well. Yellow light tends to be less useful overall for many photosynthetic organisms, but humans can see it well so it is often incorporated into the spectrum.

Color temperature is sort of a combination of all of the different colors in a light. The temperature somewhat refers to where on the spectrum the light appears to the eye. The spectrum (infrared-red-orange-yellow-green-blue-indigo-violet-UV) when roughly equal appears white. Lower color temperatures are closer to the red end, and higher ones are closer to blue. Here are some we commonly see in the aquarium trade:

6,500K: Yellowish white (sometimes called "warm white")
10,000K: White (sometimes called "cool white")
12,000K: Cool white, slightly bluish
14,000K: White/blue, common for coral tanks
20,000K: Very Blue, also used for corals

The color temperature DOES NOT tell you where the peaks are. Therefore it doesn't tell you much about PAR either. Look at those graphs for the spectrum and think about the organisms you are growing. Most plants have similar requirements, as do many corals.

Over time, the spectrum of a bulb can shift from when it was new. That is why many people advocate changing their bulbs before they burn out. These shifts in spectrum can make the light have less PAR (or really PUR, but I'm not gonna get into that now) for the plants, but it may be perfectly suitable for certain algaes.

Hope that helps. I'm too lazy to proofread it lol. let me know if I was unclear, wrong, or missing information.

 

[Beetlebug515]

Ahhh! That is fantastic information. That should be some sort of sticky. It's bedtime for now, but I'll reply again in the morning. Thanks for taking the time to write that up.

 

[xxUnRaTeDxxRkOxx]

Maybe this will help you to some what understand what spectrums are better for live plants, plants have 2 chlorophyll stages; Chlorophyll A & Chlorophyll B, each stage has different peaks to them which the image represents. These peaks in the chlorophyll stages help in photosynthesis.

Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the "fuel" used by all living things.

(Chl=Chlorophyll)

So plants utilize certain spectrum peaks in lighting for proper growth, growth rate, etc... This is why I always go with the following bulbs for my planted tanks...

6500k bulb, 420nm actinic bulb, 12,000k white actinic bulb, and wavepoint ultra growth wave bulb
(bulbs listed above are front to back in my light fixture)

I always use T5HO quad 4 bulb light fixtures on my planted tanks, but I have a certain lighting schedule that I follow...

8am - 2 front bulbs turn on
10am - 2 rear bulbs come on giving me a " light burst" to simulate high noon lighting
2pm - 2 front bulbs shut off
4pm - 2 rear bulbs shut off


Here's why I go with a WavePoint Ultra Growth Wave bulb

The growth wave bulb is specially designed to accelerate growth in live plants, and in a saltwater reef tank. It peaks around the same color spectrums as chlorophyll A & B...

PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more or less with the range of light visible to the human eye.

Photosynthetically Active Radiation (PAR) is the amount of light available for photosynthesis, which is light in the 400 to 700 nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day.

Levels are greatest during the summer at mid-day. Factors that reduce the amount of PAR available to plants include anything that reduces sunlight, such as cloud cover, shading by trees, and buildings. Air pollution also affects PAR by filtering out the amount of sunlight that can reach plants.

 

[Pomatomus]

As I briefly mentioned before, PUR (photosynthetically usable radiation) is more useful than PAR, but is difficult to determine because it varies by species. It is the portion of PAR that can be used by the given organism, and is basically the PAR range minus the middle portion (mostly yellows). It gets more complex than that but that's all I'll mention here.

TBH I saw the best growth in my plants when I used 10,000K bulbs exclusively. I have also tried color max, actinic, and 6700K bulbs as well but they just didn't produce as many plants (or as large). Since I sell my plants to multiple stores I will be returning to 10,000K's ASAP!

Light outside the PUR ranges will be more likely to produce algae as opposed to plants, depending on the alga.