Actinic purely aesthetic??

[Mummer]

I just got done reading a bunch of stuff on the web saying actinic light is less desirable for the health and growth of corals than full spectum daylight, and is really only used to please the eye. Is that so?

 

I am running a 4x24 watt setup that currently has two 50/50s and two actinics. Would my corals be better off if I switched out the 50/50s to full daylights? Or switched out an actinic for a daylight, or for a 50/50? In other words, would it be better to have a higher ratio of daylight to actinic??

[el pez]

even if so, isnt the point of the reef itself to be asthetic? personally i prefer the look actinic blue versus daylight. whichever you prefer to look at is probably best. plenty of people run actinics and have healthy corals.

[Undertheradar]

Depends. I have heard both sides of the story...from what I have put together...it depends. Actinics DO have an output...or a PAR (photosynthetic radiation). Many Euro reefers leave theirs on 24/7 for increased coral growth. They do have an output in the 420-450nm range...very blue, or course. As to if this has an impact on anything in your tank is rather subjective.

 

If this is actually helping your corals or purely for viewing purposes depends on your other lighting. IF your other lighting peaks in the warmer spectrums, yet lacks any peaks in the blue ranges (like a 6500K bulb), an actinic bulb is used to balance the lighting spectrum. Considering underwater species are subject to preks of light in the blue spectrum which other bulbs alone do not have, actinics can be used to make a more complete spectrum to suppliment the other incomplete bulbs (6500K, 8800K, 10,000K even).

 

What happens if you dont have alot of blue? Well, that depends too. Algae and other plant based organisms use the redder parts of the light spectrum for growth...corals, IME, seem to like bluer (which makes sense considering they are under water). In tanks where I had very little blue, the corals were not as colored, and algae was more prolific cuz it had an advantage over coral due to the spectrum. When I swapped out bulbs for the bluer...the corals started turning bright colors, and the algae growth slowed down. This isnt always the case, but in my case it was. IME, the blue part of the spectrum had a big impact not so much on growth, but a huge impact on the coloration of the coral...not just because of the light either. The corals pigmentation was much better under 14-20,000K than 10,000K alone.

[M0E]

Actinic supplement isnt purely aesthetic, but certainly isnt necessary for happy and healthy corals. As hobbyists, we already provide a much bluer spectrum even with 10000k, being the sun is around 6500k in the tropics.

[stack]

yes the sun is closer to 65K at the surface, but 20ft underwater where the corals live it's the blue spectrum that survives.

[ccjung]

When you are dealing with Flourescent Tubes vs. MH, the game is different.

 

Most articles, namely the ones by dana riddle describing the difference between 6500K and 20000K bulbs refers to MH bulbs, which are capable of emitting in all THREE photosynthetic bands of light, namely, the blue (420-470nm) and the Yellow/Red bands. In that situation, the MH bulb, whether 6500K or 20000K emit enough light in the lower actinic spectrum to make a difference. Here, color temp is more about asthetics.

 

Due to photoadaptation, corals have developed higher efficiencies at converting the "actinic" light into energy, since that is what penetrates the water.

 

With Flouro's unfortunately, the bandwidth of light is much lower and therefore, we often supplement the Daylight bulbs with Actinics.

 

In my experience, I have found that a key to good coral health when dealing with flourescent lighting is to keep the actinic content from 25-50% of the light.

 

This is always up for debate, but is a key point to recognize when doing research that MH is spectrally different from PCs.

 

Hope this helps

 

Chris