Using Actnics to simulate dawn and dusk?

[overanalyzer]

OK - I've been thinking about this for a while and with two threads currently discussuing how much light and which lights turn on first and how we simulate dawn and dusk ...
I currently have a logical delimma (regardless of type of lights used):
1. Actnics are used to provide blue light so it will penetrate deeper into the tank
2. We, as humans, see the blue light as dawn and dusk
OK - so if these two statements are true then when we simulate dawn and dusk with the actnics then we are actually providing more light to the bottom of the tank than a normal reef would get.
Plus we are lighting the tank in reverse - meaning the stuff deeper in the tank gets "blasted" so to speak with blue light and does not "wake-up" slowly.
Logically we should have a low level white light coming on first to light the very top of the reef, then increase the lights to go deeper and deeper into the reef.
Thoughts? Am I over thinking this??

 

[jackson_uk]

for some reason i have got stuck in my head that the sun is more intense when it is low....Bet im wrong, someone prove me wrong please.

 

[overanalyzer]

Originally posted by Jackson_UK
for some reason i have got stuck in my head that the sun is more intense when it is low....Bet im wrong, someone prove me wrong please.
OK the world is mostly round - so the sun is most intense when it is right over your head .... so when it is rising and setting it is farther away from you .... when it is right over head then the two are closest - not that they are any closer or further away ....
So Kip - is what we are doing good or bad for corals?

 

[fulcrum]

The sunlight refracts through the atmosphere, like through a prism. It is also scattered by particles of water in the atmosphere. It changes intensity and color depending on the time of day (i.e. the angle of incidence with the atmosphere, and the distance it travels through the atmosphere). When it is overhead, there is the least amount of refraction, and interference therefore the fullest intensity and spectrum of light is transmitted to the surface (or reef).
Without bulbs that change their spectrum there is no way to fully recreate the differential spectrum of light that naturally occurs at dusk and dawn.
I thought the dusk and dawn effect was based solely on the amount of light being put into the tank. The idea being If you ramp up slowly, it simulates a gradual increase in intensity percieved by the tank, so you dont just shock your system by flipping on the light.
We know that full intensity light is not natural for more than the "bright sunlight" hours of the day (9-6 or so). I think you would not want to run all your lights longer than this. If you can run "dimmer" lights only for a little while before and after it allows this ramp up/down time.

 

[jim672]

overananlyzer,
Thanks for posting this. I've been thinking about this ever since I read someone's post that actinec/blue light penetrates deeper than the white light.
It's a particular dilemna for me because I do have timers on my lights and I do have the actinics come on first and off last. The dilemna is because.......as soon as my MH goes off...... all of my corals start to shrink. That includes my bubble, hammer, frogspawn, star polyps and even my mushrooms.
If the actinic light is MORE intense, why do the corals seem to act the opposite?
Jim

 

[fulcrum]

Actinic light penetrates to a deeper depth because of its wavelength.
Think of it like sound frequency. The stereo next door may be equally loud on the bass and treble. All you hear is the bass, because the frequency (wavelength) allows it to penetrate the walls. Hi frequency sound (short wavelength) is deflected by the wall.
So while actinic may penetrate farther, MH may provide the spectra the corals need to metabolize nutrients. Because MH is much brighter (higher intensity) plenty of light of the right spectra penetrates to the depth of the corals.

 

[hookedonreefs]

jim672, this is my "semi-newbie" explanation for you. Actinics are not necessarialy more intense. They just have longer wavelengths, and as such, can permiate deeper into the sea. That is how we can keep bottomer dwelling creatures happier, by providing the type of light that they get in vast amounts.
As to why your corals shrink, white light is an amalgamation of all the spectrums of light put together. As such when the MHs are on your corals are getting the blue spectrum as well as the others at a VERY intense amount. When the MHs turn off they lose all that light and are left with a monimal amount of blue to work with.
It makes sense to me, if it's wrong please let both jim672 and I know.

 

[overanalyzer]

Fulcrum - thanks for the moredetailed explanation ....
so if the shorter wave light does not penetrate as deep should we not - if we truly wanted to simulate the dawn to dusk for hte reef - use those first - then actnic - then our brightest lights ....
example:
NO regular light comes on
then VHO 50/50
Then Actnic
Then MH
then reverse off?
or skip the MH and do a regular NO, the a 50/50 then full actnic.
So I guess my question truly is:
is there any harm or benefit to having the dawn to dusk affect geared towards humans and not towards the reef??

 

[jarvis]

Your missing the point of white light having all colors in the spectrum. Yes blue is the most easily absorbed in the spectrum and does reach to deeper lenghts in the ocean however in our shallow deepth tanks I belive that it really has no real sugnificant effect on depth penetration (I could be wrong). Also since you have 1/2 your lights turn on you would not be blasting the corals by any means compared to having all your lights turn on at once.
I have been considering running my tank with full URI aquasun and mabee one small atinic on a small cheap ballast. Just for my veiwing pleasure of having the dusk and dawn effect. I like the look better of full aqua sun it just seems more natral. I still want to do some more research on the specrum the bulbs produce, but I got time before bulb replacement. Who knows mabee I will just keep my setup mix of 50/50 as is and add some 6500K halides. Im sure the corals would like that and I would be pleased with the look.

 

[fulcrum]

I think we should abandon the "dusk/dawn" terminology, and say this:
Dont flip all you lights on at once...it might shock the tank. If you can, turn your lights on and off sequentially, such that your highest powered lights are last to turn on and the first to turn off. This way, everything has time to adjust slowly to the changing light, similar to the way it would in nature.

 

[fishnerd1]

I read some article on the fact that the light reaches the reef very fast after sun rise, like within an hour its very bright, and that the shock of light is not a big issue. However,
I have my 250 watts come on all at once, and they stay on for 12 hours. My balast powers all at once so I cant turn them on gradually. Should I cut my 12 hour time down and put in a flourescent for on for a couple of hours?

 

[califishdude]

OK the world is mostly round - so the sun is most intense when it is right over your head ....
Went I took Geography i thought the world was round, so what happened in the past ten years to make it mostly round. I know fromliving in kansas it was flat and california is Bumby. Im just wondering....LOL

 

[jim672]

fulcrum, hookedonreefs, Kip, and others,
Thanks for the explanations. I was confusing intensity with wave length. I believe I understand the difference now.
Jim