# Actinic light bulbs useless for plants?



## shrimpNewbie (May 6, 2011)

So I got some coralife compact fluorescents for free but havE been told they're useless for plants was wondering if it really is useless cause I need a couple lights for my 20 L and would be awesome to add this 65 watter to a day bulb, any info appreciated


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## gagaliya (Aug 19, 2006)

Yes, actinic are useless for plants.


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## cggorman (May 9, 2009)

I disagree vigorously.

It depends on the wavelength, but plants can utilize the energy produced by the higher wavelength actinics. They look odd to my eye, but that's subjective.

The 420 nanometer bulbs are pretty close to ultraviolet and the plants don't utilize the energy as efficiently as the 460nm bulbs. Below about 420 and you are in ultraviolet territory (think blacklights). Also, as the wavelength drops, you will start to see your water cloud up as the floating particulates and microorganisms begine to flouresce visibly.

The Photosynthetically Active Radiation (PAR) range for plants is generally considered to be from about 400nm to about 700nm. There is a peak arounf 450nm, so actually a 460nm actinic bulb is extremely good for certain kinds of plant growth.


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## gagaliya (Aug 19, 2006)

cggorman said:


> I disagree vigorously.
> 
> It depends on the wavelength, but plants can utilize the energy produced by the higher wavelength actinics. They look odd to my eye, but that's subjective.
> 
> ...


That's news to me, you can grow plants with actinic? I really dont think it's a good idea though even if you could, should stay between 5000k to 12000k, i usually go for around 6500k-6700k seem to give the best result.


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## cggorman (May 9, 2009)

Balanced light would be better for proper development of the plant leaves, internode distance, etc., but that part of the spectrum is essential.


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## vespers_ (May 6, 2011)

i may be wrong, but actinics are not useless for growing plants. they are just focused in the blue spectrum (around 460nm) and don't have the red end of the spectrum that plants need too.

they only rpovide some of what the plants need versus a 6500k or 10000k etc... which have the full range.


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## wendyjo (Feb 20, 2009)

Lets say useless if that is the only light you're using, and also pretty useless if you are using it in addition to a full spectrum light.


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## shrimpNewbie (May 6, 2011)

Thanks for all the help will try trading them or saving for saltwater


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## ReefkprZ (Aug 21, 2010)

actinic light that falls withing the range of 430-460 nanometers is completely capable of allowing photosynthesis. I run 3 daylight NO and one actinic VHO on my tank. believe me when I say actinic would be a lot less popular with the marine world if it didn't allow photosynthesis. below a certain depth of water ONLY the blue wave length penetrates. after about 3 feet 60% of red light is knocked completely out of spectrum. I guess any plant growing beyond that would disagree about the importance of red light to aquatic plants. there are quite a variety of photo synthetic organisms that thrive on nearly pure actinic for photosynthesis.

Blue and green wave lengths are actually better for driving photosynthetic light down to the bottom in deep tanks. 

my tank is about 24 inches deep (to the substrate), I know that about at the substrate about 40% of the red spectrum has been knocked out. there is still plenty of yellow and green and blue to support photosynthesis but since daylights do not generally have a large amount of the blue spectrum I use my actinic to ensure there is par with penetration, for my low growing bottom plants as well as to balance the light and make it look less yellow to my eye.

In summation actinic is NOT useless for plants. I wouldn't run a tank on only actinic but my 20 long has a 50/50 bulb in it and there is nothing wrong with it. ( 50/50 is 1/2 10k 1/2 actinic)


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## JEden8 (Jan 5, 2011)

I am by far no expert with lighting but I have seen a tank grow with actinic bulbs. He had a 90 gallon discus tank setup and had several large pieces of narrow leaf java fern. The tank honestly looked amazing. The only light he uses for that tank is actinic. I don't know if it's just specific types of plants that will do ok with just actinic or what but I was actually very impressed.


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## wendyjo (Feb 20, 2009)

Well java fern will pretty much grow in the dark.


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## gimmethatfish (Jun 13, 2010)

I can concur that you can grow plants with actinic lights. I have one tank that was running actinic only for like 8 months the plants continued to grow just fine. I just switched the actinic out for a 10k and I honestly miss the blue but I'm sure the plants will prefer it.


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## Sharkfood (May 2, 2010)

If you can see light when you turn on the bulb, then it can be used for photosynthesis. Using actinics to grow plants is incredibly wasteful however. You will be using the same amount of electricity to produce relatively little useable light. It's kind of like going to the pump, paying for 4 gallons of gas, but only putting one gallon in your car.

It is true that blue light penetrates water better than "warmer" colors, but unless your tank is several meters deep, this is of little concern. 

When it comes right down to it though, the fact of the matter is that you can grow plants under actinic lights. This is true of any bulb that puts out visible light.


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