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FAQs about Light and Lighting for Marine Systems, Lamp/Bulb Selection 2

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UV Question, lamp sel. for it and K for tank itself  11/15/11
Good day everybody, Here I am back at your mercy again. I have been having a small brown algae problem. My uv sterilizer was taking care of it for months. Then I noticed it was coming back again. I cleaned out my pump because it was clogged, and put a new bulb in. I have Corallife turbo twist uv 18watt. Now here's the question. I bought a generic Uv bulb off eBay. Are they as good as the regular coral life bulbs?
<UV lights are actually ordinary fluorescent tubes without the fluorescent coating. The tubes are filled with argon and mercury gas with electrodes on each end. A high-voltage electric current runs through the gas between the electrodes. When one of the electrons from that current strikes a mercury molecule, part of its energy is absorbed, exciting the mercury. The mercury then shoots out the energy as a photon of ultraviolet or purple light.
Normal fluorescent tubes have a coating which catches these photons and emits white light, but UV tubes simply omit the coating. So as long as your new UV lamp has no coating, it should be effective.>
I have a 180 reef. Nitrate, ammonia, nitrite are at zero. ph 8.2 Salt Gravity 1.025, Temp bumps fro 79 to 81. The tank is a 180 tall 4ft long 3ft deep. It has two 150 watt 10000k metal halides and two compact 90 watt actinic. Been thinking of switching to 20000k bulbs to see if that would make a difference. What do you think?
<Higher wavelengths do help controlling algae growth but I would not use all 20K lamps if you have photosynthetic life in your system. Be better to go with two 14K MH lamps.>
<You're welcome. James (Salty Dog)>

Lighting, Skimmers'¦and a dearth of info provided -- 11/14/11
<<Hi there>>
I accidentally bought a 20k light bulb and I think I can just use it as a weaker actinic light bulb.

<<Or maybe return it for credit/exchange>>
Can I use this bulb with a 10k bulb?
<<Sure'¦though whether this combo gives the needed light intensity I have no idea as you have left out any detail of your system. Do have a read here and among the associated links at the top of the page (http://www.wetwebmedia.com/marlgtganthony.htm)>>
Also, how would I use a powerhead for a protein skimmer?

<<Not enough information to formulate a response>>
If I can't then do I have to use only limewood air stones

<<Ah'¦if your query re the powerhead is to provide the 'bubbles' for a skimmer, this likely will prove insufficient. Best to stick with the original design, or purchase a different/better skimmer>>
or can I use different ones?
<<In my experience with air-driven skimmers, most anything other than Limewood air diffusers have proven disappointing as they just don't produce a fine-enough bubble, in my opinion. You can 'make' a fairly suitable substitute from Basswood (can be found at arts-and-craft stores like 'Michaels'), if you have the tools/are a bit handy. Otherwise, I would stick to the Limewood. EricR>>

R2: Sand Bed Question (Placement, Depth'¦Lighting Too!), lighting color temp. -- 05/27/10
Hi Eric, Lang again.
<<Hiya Lang>>
Quick question for you and your crew.
<<Okey Dokey'¦and more accurately it is 'the' crew, of which I am but a humble member>>
I noticed below your correction of my 10,000k to 10k.
<<Mmm, not really a correction but rather just a different way to state such>>
I was under the impression 10,000k stood for 10,000 Kelvin.
<<Indeed'¦10,000k, 10000K, or 10K are/would be all understood to indicate the color temperature (Kelvin) of a lamp>>
Which is a temperature, but is also used to measure color.
<<And the reason for the descriptor 'Color Temperature'>>
I know from my limited knowledge of the Kelvin scale we would not be able to tell the difference between, say, 10 Kelvin, and 20 Kelvin.
<<Ahh, I think I see what you are getting at now. In the literal sense, you are correct'¦but 'in the hobby,' 10K and 20K are accepted and understood (mostly [grin]) terms for 10000K and 20000K, respectively>>
So what is the accurate way to describe these lights over our aquariums? Is it 10k MH, or 10,000k MH?
<<Either, as explained. My apologies for the confusion'¦ Cheers, EricR>>

CRI, Photosynthesis 6/25/09
Hi Crew,
<Hello Joey>
Why is it that, "for the sake of photosynthesis in aquaria, CRI values of ninety (90) or greater are called for?" (Fenner). If a bulb has high intensity in the short red and blue spectrums, and a color temperature of
5000K+, what makes a high CRI value necessary for photosynthesis? Or do those other measures relate to/determine the CRI? I ask partly because I have gotten the impression, digging around the internet, that a high CRI usually means an unattractive, harshly white light.
<CRI (Color Rendering Index) is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source, such as the sun. CRI by itself does not necessarily indicate what the color temperature of the reference light source is, and that is where Kelvin temperature comes into play.>
Thanks for the guidance,
<You're welcome. James (Salty Dog)>
Joey E

Re: CRI, Photosynthesis 6/27/09
Thanks for the response.
<You're welcome.>
Are you saying that the perfect 100 CRI bulb renders them the color that natural sunlight would, because the bulb's light illuminates them so,
or that the light, through photosynthesis, causes them to become the color they would be if sunlight were photosynthesizing them? If you mean the former, as I suspect, then what role does the CRI value play in photosynthesis in the aquarium? Will my plants not grow as well with a low CRI value, or is the concern merely that they will not be rendered they way they naturally would?
<If you read my definition of CRI again, as I mentioned in the previous email, it says nothing about photosynthesis. We can have an 8 watt bulb with a CRI of 98, but it isn't going to do too much for photosynthesis in a 55 gallon tank, not enough intensity and lumens.
What we generally look at now is the Kelvin temperature and wattage of the lamp. Many moons ago, when standard fluorescents were our only choice of lamps, CRI was a factor, as it was a good indicator of the usefulness of the lamp for plant growth. Back in those years, Vita-Lite manufactured a twisted fluorescent tube that had a CRI of 91, and a Kelvin temperature of 5500K, and was widely used
by aquarists for growing plants.>
Thanks for working through this,
<You're welcome. James (Salty Dog)>
Joey E

Lighting query (again) - LED's and colour temps 4/19/09
G'day crew
<Hello Leon.>
Hope today finds you well. As always thanks for a fantastic service, and thanks in advance for whoever is on duty today for the advice...once again on my "favourite" topic: lighting.
<Today was fine, Scott V. with you tonight.>
First question is regarding colour temperatures (K), and is this: "If colour temperature is based on changes in colour when heating a black body radiator to a specific temperature, why do some bulbs (often from reputable manufacturers) which have the same colour temperature rating give off a visibly different light colour?"
<Simple, they are not accurately rated.>
A good example here is 10k tubes...just about every brand has their version. But if we take a couple of high-end 10k lamps - say an Arcadia original tropical lamp and an Aqua Medic Ocean White - we see a marked difference. The Arcadia has a slight pinkish/purple look to it, whereas the Ocean White is a very crisp, bright white. Then compare these with a more mid-range product such as Catalina PC's and you'll find that the Catalina 10k's appear slightly more yellowish.
To take this one step further I'll use another mid-range bulb, the Hagen Power Glo, as an example. It has a K rating of 18k, but has a visible pinkish colour to the light...not at all the very blue light that you would
expect from a bulb of this temperature.
Is this all to do with the human eye's sensitivity to various spectra, or is it creativity from the manufacturers' marketing departments, or is there some other standard or factor that I'm simply not aware of (which I think
is probably the case)?
<No universal standard and lack of actual spectral testing.>
Second questions is regarding LED lighting...
There are a few, apparently good, products slowly becoming available in Australia. I have been doing a bit of reading about LED systems in general but a lot of the info I've been able to find (including some interesting commentary on WWM) is anywhere from 4-10 years old. The general message seems to say "promising technology, but expensive and still having some trouble with light quality and spectral range"
<My sentiment, I do feel it will replace all in the years to come.>
Given how quickly technology improves I'm just wondering what the current status of LED technology is? For example, has the spectral quality been able to live up to fluor/MH standards?
<Sort of, it all depends on what bulbs the LEDs are compared to...for my money not there yet.>
Do you know of any recent comparative studies?
Also, can you point out some "reputable" products on the markets which I can do some further research on?
<PFO Solaris fixtures are the standard thus far.>
In Australia we tend to be flooded with products from the Chinese market, some of which are actually really good value-for-money, others which are just a complete waste of time. This link (
http://www.oceanus-light.com/lumenaqua36.html ) is one such product, though I'm not sure which category it fits into yet. The idea of a variable spectral range is very appealing, but I question the reliability of the
data as it all appears very market-orientated with a distinct lack of scientific info to back it up (e.g. spectral output graphs).
<Well, there are many DIYing these LED fixtures nowadays too.>
Thanks again
Leon (Brisbane)
<Welcome, Scott V.>

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