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  1. #1
    Moderator Krugar's Avatar
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    What you should know about lights

    But didn't know you should ask. Before reading further, I'm not making any recommendations on what lights to use when. My goal is to set up up so you can have an informed discussion on them.

    T5/T8/T12, power compact, NO, HO, VHO, MH, stop the world I want to get off... what does it mean?

    Okay fist off T means Tube. The number after that is the diameter of the light in 8ths of an inch. So T5 is a tube 5/8" in diameter T12 is 1.5".

    NO - Normal output. Good for fish, but not much else.
    HO - High output. Through the magic (TM) of T5s HO lamps may be good for everything if your tank is shallow enough. (under 18")
    VHO - Very High Output. Usually a T12, these are the "old stand by"

    MH - Metal Halide. This is a high intensity discharge (like a street lamp) light. Other HID lights you may be familiar with are Mercury Vapour and High Pressure Sodium (those yellow street lights.) MH lamps are used for marine tanks because they need the least tinkering with to get the colour spectrum we want.

    Power Compact - The other fluorescent tube. Inexpensive, small, reasonably low heat, these are good lights for specific applications. (all lights are only good if they're matched to the application.)

    Okay some fun fluorescent facts.
    You can read the stamp on a tube almost like a tire. There's wiggle room in the spec but say your lamp was stamped with:

    F96/T8/735/RS

    This means:
    F -> fluorescent
    96 -> wiggle room time. Either length (inches) or nominal wattage.
    T - It's a Tube!
    8 - Diameter in 8/ths of a inch. A T5 therefore is 5/8" A T12 (VHO) is 1.5"
    7 - CRI index of 70 - 79 (yuck.)
    35 - colour temp (way yuck, 3500K)
    RS - Rapid start. Others here might be HO, VHO, IS (instant start), or ES (energy saver)

    A 48", 110W lamp would be:
    F110/T12/???/VHO or F48/T12/???/VHO I'm at the office, I can't check my URIs. Anyone want to test me?

    This is the specification all lamps are sold by. Length, nominal wattage, size, colour (cri). That's what's important to the rest of the world, that's what's stamped on the lamp. The next most important item would be lumens. Normally stamped on the outside of the box.

    Colour is measured in degrees Kelvin. It's the temperature a black body radiator has to get to to emit that frequency of light. A simplification would be you have to heat something to that level to get that colour. incandescient lights are reasonably close to black body radiators so the colour temperature works. Everything else is a guestimate by the manufacturer. This is called the correlated colour temperature or CCT.

    The manufacture gets to pick the temperature closest on the curve for their lamp. This is why 2 14K lamps from different manufacturers give radically different results over your tank.

    If I haven't already put you too sleep here's a more detailed explanation: http://en.wikipedia.org/wiki/Color_temperature

    CRI is the Color-rendering index. In a nutshell this is a score out of 100 as to how well the light accurately reproduces colour. Higher means "truer" colours. Not used over much for aquariums.

    More info: http://en.wikipedia.org/wiki/Color_rendering_index

    Lumens or flux is how much light the lamp puts out in the visible spectrum. Visible to humans, not fish, coral, or algae. This is measured at the light and decreases inverse to the square of the distance, when your media is air. I forget how it decreases for water, but odds are you don't have pure water in your tank anyway. Let's just say "more" and leave it at that. You can usually find the initial and design (after burning for a while) lumens of a bulb on the manufacturers website. All things being equal, more lumens is better.

    Lux is how many lumens / square metre. 1 lux = 1 lumen / square metre. Lux is actually more important, but the manufacturer can't measure it for you. This is how much light is on the surface of an object (your coral for example) Lux requires you getting wet to measure it in an aquarium.

    PAR is more important still. PAR is Photosynthically Available Radiation. This number is what your coral & algae are really concerned about. The more par the more they have to "eat". Manufactures again can't tell you what the par will be, it requires somebody getting wet in your tank. As with lux it will change based on how far away the lamps are, what reflectors you're using, what kind of cover you have, water clarity, amount of water, possibly SG, age of the lamps, and maybe even if there's a solar flare right now. Bottom line is it needs to be measured. Without enough PAR, your photosynthetic animals starve to death. Adding more lights does not affect PAR, it changes how far (length and width, not depth) that PAR goes. Adding more powerful lights may increase PAR if the light output is in the right spectrum. Think about a black light vs a grow bulb.

    So what does that leave the average aquarist with? How the heck to you figure out what kind of lamp & ballast you should or shouldn't buy?

    Easy. Ignore everything I just wrote. Forget it, it's really not important unless you're a geek like me.

    1) Figure out what animals you want to keep. If you only want fish, none of the above matter. You only need enough light for everyone to see. Plan it first. Measure twice, cut once.

    Softies, lps, sps, all have different light requirements. An sps tank will require a very different set up from a tank with a few fish & some mushrooms. Why bang your head against the wall needlessly? It's almost like researching the best dog food when you're about to buy a canary. A better analogy might be planning out your flowerbed. You can tell who's really planned it & who's thrown a bunch of stuff together.

    2) Figure out how big of a tank you're going to have. For your lights how deep is more important than how long. How deep is how powerful the lights need to be, how long and how wide = how many lights you'll need.

    How big of a tank you'll need also depends on what you want to keep. You can't put a whale in a 12" tank. 1 & 2 are dependant on each other. If you only have room for a 12" long tank that will limit what you can do in step 1.

    3) Now start the holy lighting crusade. I'll give you a short cut, no light is better than another any more than a hammer is better than a screw-driver. You need to know what you want to do before you reach into the tool drawer or you might find yourself with a #2 robinson and a box full of nails. Same thing for lighting.

    There are only 3 requirements for lights:

    1) Keep the animals alive. If your animals eat rather than being photosynthetic, you're done any light will work. The more light demanding the animal the more powerful the light required. If you name the coral, you'll get at least 3 different suggestions on lighting requirements.

    Keep in mind though that most of this information is anecdotal. Just because somebody's kept a clam under PC lighting for 3 years doesn't mean you'll be able to. People occasionally survive skydiving without a working parachute, not recommended but some people can do it.

    2) They need to look good. I can't help you here, that's your personal choice. Once you've figured out the type of lights, the colour temperature and the type of fixture really isn't terribly important. Yes you'll likely have better growth from a 6500K MH lamp than a 20000K lamp at the same wattage, but both will keep your coral alive and growing. What's more important is what you want it too look like.

    3) They need to fit your budget. Again that's personal. My wallet is definitely a different size from your wallet, likely much smaller. Once you've determined what kind of lighting you require, fitting it into a budget is much easier.

    So where does all of this get you? Well hopefully it will have everyone asking more informed questions. Frequently there's on-going debates as to what's the best lighting. I dunno, what's the best tool in your tool box? What's the best car? It's all extremely situational and subjective.

    If you've taken the time to read through this rather lengthy post, hopefully more of what the lighting geeks (like myself) are saying will make sense.

    Cheers!
    There is nothing so permanent as a temporary measure.

  2. #2
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    Thank you.

    Being new to this, I've always questioned my lights.

    But after reading this I think I'm ok with my 4 x 24w 6500k compacs. and 15w actinic over my 20g high.

    Maybe more actinic would help with the color?

    Thanks for the long post.
    P.S. I'm french so I never make any typos......they are actual mistakes :sorry:
    I'm not in a rush.....but I am on a budget! :bigcry:

  3. #3
    Moderator Krugar's Avatar
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    The 6500K better growth example I gave is based on a 6500K MH lamp having a higher PAR than a 20000K lamp. It may not be as big of a difference for power compacts.

    IMHO that will be pretty yellow although the actinics will help balance it out. My preference would be for 10 - 14K lights with true actinics, but it's up to you.

    Trying different lamps is part of the game. You're not going to be 100% sure you'll like that combination until you've tried it over your tank, in your house. It's like owning a car for a year vs. test driving it.

    Cheers!
    There is nothing so permanent as a temporary measure.

  4. #4
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    Very fun post. Thanks.

  5. #5
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    Should be made into a sticky!

  6. #6
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    Quote Originally Posted by Krugar
    IMHO that will be pretty yellow although the actinics will help balance it out. My preference would be for 10 - 14K lights with true actinics, but it's up to you.
    But other then looking yellow......they are still ok for my mushrooms......right?
    P.S. I'm french so I never make any typos......they are actual mistakes :sorry:
    I'm not in a rush.....but I am on a budget! :bigcry:

  7. #7
    Moderator Krugar's Avatar
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    My mod powers don't work here, if it's going to be sticky it's up to somebody else.

    I wanted to edit in a comment on PAR, many manufacturers do provide a PAR number. And the amount that it will be different in one aquarium to another isn't that big of a deal unless you're comparing a nano to a 500G tank.

    To actually find out the real PAR in your tank, you have to get wet as I mentioned and it can vary as I pointed out. Probably not terribly significantly though. Having the right lights is more important IMHO than fine tuning the PAR.

    YMMV, I was trying to get the basics across and make it somewhat entertaining.

    Cheers!
    There is nothing so permanent as a temporary measure.

  8. #8
    Moderator Krugar's Avatar
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    Quote Originally Posted by alparent
    But other then looking yellow......they are still ok for my mushrooms......right?
    They'll be fine. You may have some colour loss though. The store likely has MH lights with true actnics to make the colours really pop. Under PC lights, over time you may loose the intensity.

    This could range from a faded appearance to turning brown. It doesn't hurt the coral if it happens, it just doesn't look as cool.

    Cheers!
    There is nothing so permanent as a temporary measure.

  9. #9
    Senior Member bebitte70's Avatar
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    This is very helpful for people looking for lights. It should be made into a sticky.
    55G CSS 3004, 2 Seio 620, 220WT5HO lighting, Yellow tang, yellow tail damsel, 2 clownfish, 1 shrimp, pulsing, soft corals.

  10. #10
    Senior Member Ricepicker's Avatar
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    great post krug, but, i dunno man, don't u think... u should... uh... work?

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