Actinic lighting and plants

ahill3780

It is my understanding that actinic lighting emits a UV range of around 420nm to 460nm. I have heard that this particular spectrum of light is greatly beneficial to cloraphyl (?) in the tank which effects photosynthesis. In theory the addition of actinic lighting in a planted tank would benefit the plants.

My question(s) to you all is, how accurate is this information, how beneficial would this be and what would be the most visible effect? (greater color, faster growth, etc?)

Any information you guys can provide will be of great interest to me, and others as well.

Jay

There is a ton of misunderstanding, confusion, and wrong information available to the planted tank hobbyist where it comes to lighting.

Let me try to back into Aaron's question, as it is a very complex and difficult subject. A degree in physics would help and I suspect most of us are in the "don't have" boat.

Sooo..this information is going to be rendered newbie friendly.

Bottom Line: We are really dealing with three things.

1. Light Wavelength Measurement = nm nanometer 1 billionth of a meter

2. Photosynthesis = in this case, plant growth (Carbon uptake)

3. Kelvin Rating = The color of light used and appreciated by the hobbyist.
Personal Preference

It is generally accepted in the planted tank community that light in the range of 400 - 700 nanometers will grow plants well, 660 - 700 nm will drive photosynthesis even faster. These numbers should be available on the package or from the distributor, or at the manufactures web site.

The light does not have to be, and this is important, from super expensive "plant growing tubes" with rare phosphors designed to deliver exactly the right wavelengths for optimal plant growth and health. Come here kid I have these $70tubes I'll let you have for $60.

#2 If the tubes are providing at least 2 watts for every gallon of tank water and they are in the 400 - 700 nanometers parameter then photosynthesis will happen, plants will take up carbon and grow.

Color of the Light.

Plants reflect back the colors of light they do not adsorb. Usually the red spectrum spike and the blue spectrum spike are used and green is reflected back. That is the way you and I see color.

Light bulbs are rated with what is called a Kelvin number. A Kelvin number is assigned to the color of a (controlled laboratory open Flame) the color can range from yellowish to blue white. Kelvin is refered to as color "temperature" ...get it

5500K = to our eyes a yellowish tint
7500k = to our eyes produces light approaching white
10,000k = to our eyes crisp white light, slightly blue
10,000 20,000K Intense white light needed to deeply penetrate water and reef tanks.

Actinic blue light: In the planted FW aquarium world is light designed to provide energy in the blue spectrum. Will it hurt plants, no. Is it beneficial, shrug.

Lots of planted tank folks use blue actinic mixed with other k temp. tubes to alter the color of the light in the tank to what they feel is a more aesthetically appealing look.

UV light has very little penetration capability in fw tanks and is largely ignored. That is why a UV sterilizer has a very small distance between the water and the UV tube.

Please keep in mind that light is only one of three essentials that must work together for plant success.

The other two are...
1. Nutrients
2. A source of carbon

Hope this ramble helps.

Regards,
Jay

wl_keller

I recently purchased a compact flurousescent light fixture for my 29 gallon tank. The fixture came with a 10000K bulb and an actinic bulb. I wasn't sure about the actinic light since from what I've read it's not in the right color range for plant growth.

But rather than replace the brand new bulb that was already in the fixture, I gave it a try and so for it seems to work well. So far the plants have really responded to the light and I haven't had too much of a problem with algae. I'm not really fond of the color, but I want to wait until the plants get bigger before making a decision to replace the bulb or not.

Jay

It's the 10000k white light the plants are responding to. The blue is neutral, neither good or bad for plant growth.

Regards,
Jay

wl_keller

So if I replace the bulb so that it has two 10000k or 6700k bulbs, would I have twice as much effective light?

It would appear that if the actinic light is neither good nor bad, I probably should replace the bulb since plant growth was the main reason I replaced the lighting in the first place.

Jay

I would unless you are obsessed with the color.

Jay

wl_keller

Not really too wild about the color.

But after years of working with low light plants, I just want to every last bit of 65w compact flourescent power put to good use.