Actinic lighting.

firstman

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10 Sep 2008
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Hello all, have a lighting question for you. I have a 40 gallon newly planted tank with CO2. The light that I am using is a Current Dual Satellite w/ two 65w bulbs. One is a 6,700k/10,000k and the other is a 420nm/460nm Actinic. Do you know if the spectrum from the Actinic is good for freshwater plant growth? I have seen sites stating that they are good for Marine Coral growth and also for freshwater, but most reading material talks about the benefits for Marine. Do you think I should keep the Actinic or replace with another 6,700k/10,000k? Or get a 6,700k only? Any info or comments would be greatly appreciated. I don't want to buy another bulb when this one is still new (it came with the fixture) but will do what is best for the plants. :) Here is a link to a spectrum graphic if it helps.

http://www.current-usa.com/repository/images/1167352083.jpg
 

JamesM

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17 Apr 2008
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The BIG End, South Wales
Apparently, the kelvin rating isn't important to plants, so go with whatever suits your eye. Check the pinned topic in this forum for a few pics :)

Welcome btw :)
 

Garuf

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30 Oct 2007
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Leeds.
Actinic lighting is useless over a planted tank, it's used to promote coral growth. Coral is an algae...
The best lighting would be something in the 6700k region thought it's down to personal preference, generally speaking anything from 5000k to 1000k is fine.
 

JamesC

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3 Jul 2007
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Bexley, Kent
Some people I know of use actinic lighting to great effect over a planted tank. Kelvin (K) rating often has no meaning at all to what the light output actually looks like and so you shouldn't go by this figure alone. Some of the best tubes I've ever used are 10K tubes from GE - http://www.lampspecs.co.uk/Light-Bulbs-Tubes/Aquarium-10000K_2. Generally most people, me included, go for a mix of tubes with different K values. It may take a bit of experimenting to get something you like which is why I did this thread to help - http://ukaps.org/forum/viewtopic.php?f=50&t=555

James
 

ceg4048

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Chicago, USA
Garuf said:
Actinic lighting is useless over a planted tank, it's used to promote coral growth.
This is completely untrue. Any light in the visible spectrum is useful to plants. It turns out that as light enters water, different wavelengths with different "energies" will penetrate to varying depths. Red light (630-780 nanometers) penetrates only to about 15 meters, while blue light (420-490 nanometers) can penetrate to as deep as about 250 meters. This is why the ocean appears blue.

Actinic bulbs peak somewhere in the 420 nm range. Any plant can use blue light, not just algae. In general, red light stimulates photosynthetic carbon fixation which is incorporated into glucose, while adding blue light causes a metabolic shift so that the fixed carbon is used to synthesize organic acids, amino acids and proteins. As long as the intensity (i.e Photon Flux Density) of the light is sufficient to fix carbon from ambient CO2 the wavelength within the spectrum is irrelevant.

Garuf said:
Coral is an algae...
Corals are not algae. They are animals who have incorporated and thus share a symbiotic relationship with zooxanthellae algae. Since most corals are found in shallow waters below the red light penetration zone it is assumed that this blue wavelength is optimal for the zooxanthellae algae. This does not automatically mean that only algae can use blue light.

The best light therefore has nothing to do with what color or Kelvin rating the bulb has. Kelvin ratings are totally and completely meaningless. In fact the bulbs these days are not even accurately rated with the correct Kelvin rating. It's actually a joke. Best light has only to do with what our eyes perceive as an aesthetic. Therefore if firstman finds his current combination adequate aesthetically then there is no reason at all to spend more money getting different bulbs. Having said that however, note that the human eye is not very sensitive to blue light and they may make the tank appear dim and colors of the plants to be slightly off.

Cheers,
 

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