# Actinic Lights Question



## George02 (Jan 11, 2007)

Hi guys,

Question about actinic lights, just as the title says. I know this has been talked about, so please don't yell at me, as I did do the search. Problem is, I can't find any definitive answers. Basically, from everything I've read, I see 2 opinions.
1. Actinic lights do absolutely nothing for freshwater plants and are only used for aesthetic purposes.
2. Actinic lights will cause algae.

I have a 20gal setup with dual-bulb setup of 65W 6,700k/10,000k. I have these lights on for 8 hours a day and I'm dosing with Seachem ferts following the dosing schedule they provided on their site.
The lighting fixture also has Dual Actinic 420nm/460nm setup, which I would like to use at night time after the daylight lights go off.

So the question is will I have problems with my tank if I do this? Does the photosynthesis continue in freshwater plants with actinic lights?

Thank you very much.


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## supersmirky (Oct 22, 2008)

Hi George

Were you planning on doing a limited actinic lighting period? If not, your fish health will go down with them not having any adequate sleeping periods.

I've been running actinic over the last week as I wait for my new bulbs to come in, and I have noticed increased algae growth. I can tell my plants are not doing great under this light but its just a temporary fix for me.

My understanding is the actinic lights are not in the range for chlorophyl to utilize.


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## supersmirky (Oct 22, 2008)

Here's a very informative post on lighting if you haven't read through this one already

http://www.aquaticplantcentral.com/forumapc/lighting/38014-lighting-spectrum-photosythesis.html


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## George02 (Jan 11, 2007)

supersmirky said:


> Hi George
> 
> Were you planning on doing a limited actinic lighting period? If not, your fish health will go down with them not having any adequate sleeping periods.
> 
> ...


I was only planning on running them at night for a couple hours (2-4) after the normal daylight lights go off, purely for viewing purposes, because the tank looks really nice under those lights. But like I said, I was worried if that would hurt the plants or fish or cause algae.

Thanks


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## freydo (Jan 7, 2006)

George02 said:


> Hi guys,
> 
> Question about actinic lights, just as the title says. I know this has been talked about, so please don't yell at me, as I did do the search. Problem is, I can't find any definitive answers. Basically, from everything I've read, I see 2 opinions.
> 1. Actinic lights do absolutely nothing for freshwater plants and are only used for aesthetic purposes.
> ...


well you answered your question about photsynthesis with opinion 1, and as supersmirky mentioned, it causes algae. he's also correct in saying that having the actinic bulbs on after your photoperid, will mess up your fish's internal clock.

a few people have asked if these bulbs can be used for a night light. the short answer is no. it's still a regular bulb, just at a different spectrum than what is needed for plants. it's like having a desk lamp pointed at your face when you're trying to go to sleep.

why not look into setting up a proper night light with a single LED lamp? many people do that here using a blue LED, and it gives you just the amount of light to view your tank, and it does not disturb the fish anywhere near like the actinic bulb.


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## Valthenya (Feb 11, 2009)

I had a marine bulb that was half and half on my new tank before i got my new bulbs in and i def noticed a diff in plant health/growth when the new lights came in


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## George02 (Jan 11, 2007)

Freydo, the light fixture actually has 2 night LED lights. Unfortunately, my cats chewed thru the power cable for them  I'll get it fixed though.

Thank you very much for answering my questions.


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## supersmirky (Oct 22, 2008)

Getting it fixed would definitely be a cheaper option. Sounds like you should be able to just strip the wires and put them back together with electrical tape


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## Newt (Apr 1, 2004)

Actinic are SW bulbs. They are designed to replicate deep ocean light. 
They emit light at a specific wavelength > 460 nanometers. If you look at the gif below you will see that this is just beyond the spectal action for chlorophyll photosynthesis.









Sure, you will get some plant growth as most 10000K bulbs have light emissions within the range for plants to easily photosynthesise. The added blue light will also cause DOC-bound iron to be released via photoreduction of iron into a form easily consumable by algae.

Look at what the europeans are using for light: 4000K to 5000K and some 6000K but rarily ever exceeding 6000K. It must be that most Americans prefer the asthetics of a high kelvin light. I for one believe we are still chasing the europeans in the plant tank field; in both equipment, knowledge and artistry.


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