Lighting an octo tank...

Discussion in 'Octopus Care' started by agoutihead, Aug 16, 2007.

  1. agoutihead

    agoutihead Larval Mass Registered

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    To me, lighting is one of the major componets in salt water.

    I have to have three stages of lighting...

    Daytime - white lights - 8am - 6pm

    Evening -blue/purple actinics - but I have read actinics aren't good for octos? Why not? Can you use any other color of light for "evening viewing"? - 6pm - 12pm

    Bedtime - Moonlights - 12 pm - 8 am (can they handle moon light spectrum?)

    Since you don't need fancy day time lighting, this cuts down on the price and opens up the selection a lot more.

    Ideally I would like to contruct some kind of retro fit LED lighting system that has all three stages of lighting.

    Would LED's work good for an octo application?
     
  2. monty

    monty Colossal Squid Staff Member Supporter

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    :welcome: to TONMO

    Lighting for octos is more about what makes the animal comfortable enough that it doesn't hide all the time than anything else; bright lights won't damage it directly, they just might make it stressed out, reluctant to eat, and so forth. Since most people want their octos to be "out and about" as much as possible, we tend to recommend lower light levels than most people use, and not to mix other animals or plants that do have specific need for bright lights into the tank.

    This depends a lot on the species of octopus as well; bimacs and cyanea tend to tolerate lights somewhat, while a lot of the pygmies are completely nocturnal and will never come out unless it's very dim. Usually, moonlights are too bright for these, even. As far as I know, no one has demonstrated that any lighting is directly bad for octos, although I worry about strong UV lights a bit, since it seems likely that in their natural environments they're somewhat protected from UV, so bright UV might damage the skin, but that's just something I wonder about, not that's been proven.

    Octos, as far as has been studied, don't see in color, so really the main issue is "does this look so bright to the octopus that it's uncomfortable?" The visual sensitivity of an octopus is somewhat different from humans, so there are things that look pretty bright to us that look dim to an octopus, and things that seem fairly dim to us that the octopus is very sensitive to. Octopus visual pigments tend to have peak sensitivity in the blue-green part of the spectrum, which makes sense, because in the water most of the red and yellow in the spectrum is filtered out once you get to a depth of more than a few feet. Because of this white, or blue-white, or purple-white lights will tend to look a lot brighter to an octopus than to a human, so octopuses that prefer to wait until dark to come out will often see all 3 of the lighting schemes as "too bright for comfort." Moonlights that are on a dimmer so that you can find the level your octo is OK with are one approach. Another one, though, is to use light that's more in the red part of the spectrum, since this will look much more dim to the octopus than it does to a human. Red LEDs seem like a good choice for this sort of thing, because they tend to produce a lot of light in a part of the spectrum that humans are much more sensitive to than octos, so they allow you to see your octo, but your octo isn't terribly nervous.

    Most octos that end up doing well as pets, though, tend to become comfortable with enough with the safety of their tanks and inclination of their keepers to feed them rather than attack them that once they are comfortable, they come "out and about" regardless of lighting... mostly, we just try to point out that a lot of reefers and fish keepers like to have very bright lights to highlight the bright colors in their tanks, which is not the lighting octos tend to be comfortable with in the wild-- even the diurnal ones tend to be out more at dawn and dusk than when there's bright sunlight, so people used to keeping their tanks brightly lit 24/7 will tend to have octos that hide and are stressed, and if you're setting up a tank to primarily be an octo-tank, it's not really useful to spend a lot on fancy lighting.

    Also, just for completeness, there are a lot of octos that really don't like camera flashes. Some get used to them, but some never do, and will run and hide whenever they see you coming with the camera as a result...
     
  3. agoutihead

    agoutihead Larval Mass Registered

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    Hmmm interesting.

    I don't know much about LED's, but would imagine there are many different colors with many different intensities.

    I would like to find a LED for the day that has a 20k look to it, white enough to light the tank, but enough blue to add some color with out freakign the octo out.

    For the evening light I will do red LED's then and for my moonlights i will try to find a purplish light that isn't too bright, but still bright enough to illuminate the tank at 3 am.

    anyone know of a good LED DIY thread or source?
     
  4. shipposhack

    shipposhack Haliphron Atlanticus Registered

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    The best thing for an octopus so it won't hide is 10k (white), or red colors. Purple will have blue in it so the octopus probably won't like it at nighttime. Reds are the way to go for night and white for day.
     
  5. monty

    monty Colossal Squid Staff Member Supporter

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    The purple might look pretty bright to an octo, since it's red + blue, and although the read peak is at the edge of its visual response, the blue is near the peak. Still, intensity counts for something, too.

    Because of the way LEDs work, the part that actually glows can only be made a few different ways, so there are only a few specific peak frequencies/ colors. But I was surprised to find out that a lot of them have a surprisingly wide frequency distribution that does overlap some with an octopus' visual pigment response. I know that with modern "white" LEDs, to get a better white, they don't just mix red, green, and blue LEDs, they actually have some phosphor that absorbs the color(s) the LEDs emit and reradiates at a lot of different frequencies. I don't know if the modern red ones do a similar trick to spread the spectrum out, which maybe is useful for most applications, but not so hot for stealth octopus lighting.

    A red laser diode would be guaranteed to be a single red frequency, but would also be very bright and would tend to do weird polarization things which we couldn't see but an octopus could (if it could see that shade of red at all) and I have no idea how the octo would react to that...

    pragmatically, LEDs are pretty easy to work with... they only work in one direction, and they need a resistor in series otherwise they draw too much current and burn themselves out. A low voltage DC power supply and a bunch of LEDs with a resistor (and maybe a rheostat as a dimmer) is pretty simple to wire up. Usually LED packages have the enough information that if you know the voltage of your power supply, say 12v, and the current the LED is rated at from the package, you can figure out the appropriate resistor size with Ohm's law, V=I R

    This guy has a lot of details of LEDs: http://members.misty.com/don/ledx.html but I'm expecting a phone call so I don't have time to look to see if he links to specific instructions...
     

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