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FAQs about Coral et al. Cnidarians System Lighting, Science & Application

Related Articles: Coral Lighting: what we know and what we don't know (mostly the latter) by Sara Mavinkurve
Lighting Reef Systems: Considerations, Organisms, Goals and Costs by Bob FennerLight/Lighting For Marine Systems, Coral Feeding, LPS Corals, True or Stony Corals, Order Scleractinia, Propagation for Marine Aquarium Use

Related FAQs: Coral Lighting 1, Coral Lighting 2, Coral Lighting 3, Coral Lighting 4, & FAQs on Coral Lighting: , Designs/Fixtures, Lamps/Bulbs, Quality, Duration & Intensity, Night-Time, Troubleshooting/Fixing, Makes/Models/Manufacturers, & Lighting Marine Inverts 1, Lighting Marine Inverts 2, Lighting Marine Inverts 3, Lighting Marine Inverts 4, Lighting Marine Inverts 5, Lighting Marine Inverts 6, & LR Lighting, Fluorescent Light 1, Actinic Lighting, Compact Fluorescents, Metal Halide Lighting, Lighting Marine Invertebrates Growing Reef CoralsStony Coral IdentificationStony Coral Behavior,

Give me light, food... good water quality!

Small Marine Aquariums
Book 1: Invertebrates, Algae
New Print and eBook on Amazon:
by Robert (Bob) Fenner
Small Marine Aquariums
ook 2: Fishes
New Print and eBook on Amazon: by Robert (Bob) Fenner
Small Marine Aquariums Book 3: Systems
New Print and eBook on Amazon:
by Robert (Bob) Fenner

Halide continued; lighting for frags.... rdg.     2/22/16
Hey Bob,
I've had darkness the past two days. Prior to that it was 12 hrs t5 while halides are out.
All of the frags I have are less than two weeks in my tank (sps).
The tank they came from were led, high intensity and were growing.
How. many hours a day shall I run the halides?
400 watt, about 12 inches off water surface, 20 inch deep tank.
Thanks for your input all along
<Best to have you search, read through the WWM archives... too many factors to go back/forth re: Species; how light adapted, PAR/PUR measuring.... B>

LED lighting       12/21/15
Hello WWM Crew,
Thanks for all the great reading so helpful. I have a question about lighting and would like your opinion, I’m not sure if my LFS is just trying to sell something 3 times the price. On a 72”tank 26”deep would 2x36” Current USA Orbit LED lighting with 144 led’s, 72 daylight and 72 actinic on each fixture total of 36 watts each, and 4x36” T5 HO 10,000K daylight be enough for various soft corals. My LFS said I would have to go up to the USA Orbit Dual Pro for corals. I value your expert opinion. Thanks is advance.
<Mmm; well.... depends (as usual...) on what you mean by "corals"; where they're placed, and what you want them to do mostly (there are a few other more minor considerations). Allow me to expand. There are some "low/er light intensity" stinging-celled groups; like Alcyoniids/soft corals, Pennatulaceans/sea pens.... and even amongst stony corals; typically the fleshier so-called large polyp corals are less light demanding (not all) than the small/er polyp species; notably the Pocilloporids, Poritids and Acroporids.... then again, not all of these share the same light-adaptability/use/tolerance.
Re the placement; of course one can "mount" their organisms "up higher" in the water column; adjust the PAR/PUR exposure therein.
And the note concerning "what you want"; refers to whether you'll be happy w/ a slower boat under wind power, or that you prefer the fast motor boat of high energy input; along w/ the necessities of current/circulation, alkaline earth and other nutrient application.
To sum up: You COULD get by easily with the first fixture here; and IF you wanted more color, growth (with the concurrent maintenance mentioned); you could use the second.
Understanzee? Bob Fenner>

JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?      2/9/14
Hello crew. JBJ has come out with a new(ish) 25 gallon LED Nano Cube with Cree emitters. What I can't seem to learn is whether this tank would work with light demanding SPS corals and clams.
Would someone there know the answer to this question?
<Likely all of us do... Are you familiar w/ WWM? Using the indices, search tool (on every page)? Bob Fenner>
Thanks, Steve
re: JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?

I had already searched via the search tool before I sent in my question.
The problem is that I got many false hits, as this product is fairly new.
I did find information elsewhere (finally) about PAR. I do not think PAR is satisfactory for SPS. Maybe James G. could weigh in.
<Will Bcc him here... A more substantive (useful) reply would have been to search re PAR, PUR and secure a test device.
Many clubs and quite a few LFSs have such for loan. This is really the only reliable way to determine suitability; other than bioassays with actual livestock. BobF>
Re: JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?

Hi Bob,
I will be happy to take care of this tomorrow, late morning.  Thanks.
<Thanks James. B>
Re: Fw: JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?      2/10/14

Hello Steve,
Bob has asked me to chime in my two cents in regards to your query. PAR can be a deceiving measurement of light for our needs as far as growing corals. Corals only use light in the range of 400-550 and 620-700 nanometers. If we take a 400 watt metal halide and measure PAR, it may well exceed 400. But the metal halide lamp will produce light in the spectrum corals do not require so how much of that PAR is available in the above spectrum. Well designed lamps will try and get as much light as possible in the above spectrum. This is why many people believe that a PAR of 200-300 measured on LEDs is not good enough but if the spectrum is fine tuned to the ranges stated above, then that would be equivalent to say a PAR of 400-600 on a metal halide lamp because the PAR reading is generated by measuring the light only in the spectrum corals require.
Having said that, it is very important to look at a spectrograph of the light produced by a given lamp or LED fixture to ensure the light being emitted is very close to the above stated range.
James (Salty Dog)
Re: Fw: JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?      2/11/14

Thank you very much, James. I am a skeptical of a manufacturer who does not
provide a spectrograph. I will inquire further from the manufacturer.
Re: Fw: JBJ "Next Generation" 24 ga LED Nano Cube ok for SPS?      2/11/14
You're welcome Steve.  James (Salty Dog)

Scleractinian Lighting and Scientific Journals--"SPS" lighting requirements - 11-12-08 Hi crew! <Evening!> I am searching the web for scientific journals or books that pertain to scleractinian lighting requirements, et al. I have had some luck searching university libraries, and have found some good articles on the WWM, but a suggestion would be great from a knowledgeable crew. <Well, if you absolutely need information from a peer-reviewed source, your best bet is Google Scholar, or reading the references in the lighting articles in past issues of Advanced Aquarist (www.advancedaquarist.com).  If you just need specific, per species information you can probably find the information here, or you can email me. I'm well versed in the lighting and lighting theory of captive photosynthetic animals (writing an article about it, actually) so I'd try my best to help> Your advice would be greatly appreciated! <Sure thing - let me know specifically what you're looking for or what you're trying to accomplish and I'll see if I can be of more service. Also, our (newish) forum is always a good resource: bb.wetwebmedia.com> Thanks!! <Sure thing - M. Maddox>

Lighting for Reef  -02/20/08 Hi, I don't know when you wrote your post on Marine Lighting. <Last time in about the mid 90's> I'm just considering a reef aquarium, and would like to know if you still prefer Vita-light and Vita-light supreme, or do you think T5 is a better plan? Thanks for your help. Brent <Mmm, for what application, desired results...? Both, all are fine technologies and Dura's products are well-engineered... There is much recorded on WWM, linked re approaches to photonic application to captive aquatics... Perhaps a re-reading/scanning there. Bob Fenner>

Lighting DOWNgrade!  9/30/05 Great site! <Glad you like it! Scott F. here today!> I know there have many question submitted such as what I am going to ask, so I apologize beforehand for redundancy.  I have just printed an article by Anthony Rosario Calfo titled, "Reef Lighting Without Controversy".  It was a helpful article as were the many WWM FAQ's I tried to sift through. <Yeah, I know that guy...He knows a few things about coral...heh, heh heh...>   My scientific vocabulary is weak at best so here are the common names of what's in our tank: Colt Coral, Green Finger Coral, Soft Leather, Hairy Mushroom as well as several other types. Pulsating Xenia and a couple different types of polyp.  My wife is 100 times better at nomenclature than I am... but I am the one asking this question.  Everything in our tank is/has been thriving for the last 5 years with our current setup.  What we want to change is our lighting.  Currently we are running two 20000K 400w radium bulbs and two 4' blue actinic VHO's all attached to the lid of a 12" canopy with two 7" fans for ventilation . <Sounds like a beautiful lighting set up for your inhabitants...Must really fluoresce them.> The lights are approx. 8"-10" from the surface of the water (tank dimension are 72x24x24).  NO!  We are not making lava! <But you could...LOL> This is how it was designed from our former LFS.  I realize that this may be a bit much for lighting.  We want to down grade to 10000K 175w or 250w.  What would be considered practical and efficient lighting for the coral I mentioned? <I'd think that a good "downgrade" would be 150w or 250w double ended (HQI) pendants, like ReefOptix or Giesemann make. Don't fool yourself, though- these pendants and configurations can throw a lot of life that can still shock corals if you're not careful.> Will there be significant shock to the marine life? <Any lighting change-up or down- can be potentially shocking to sessile invertebrates. However, if you are using the same spectrum of bulb, and carefully acclimating the animals to the new light (i.e., shorter photoperiod, possibly using screens to acclimate the animals to the new light source), you should see some good results...and a lower electrical bill!> Is it possible to direct me toward some helpful information or can you easily give me a ballpark answer?     <I'd continue to read the writings of Anthony, as well as the many helpful articles by Sanjay Joshi on reef lighting.> Thanks for ANY help you can provide, Jim <My pleasure! Regards, Scott F.>

Question About CRI Colour Temperature and UV Filtering  9/17/05 Hi Crew, <Hello Brad> I looked in the posts to try to find the answer to this question. I found the question was asked but I did not understand the answer posted. I am researching metal halide systems and found that bulbs in the 5000 to 5500K range have High 90+ CRI values. When looking at higher temperature bulbs (10000K) I notice that the CRI drops to around 65. These numbers are taken out of manufacturer catalogs for commercial bulbs. It makes sense to me that the CRI will drop the further you get away from the 5500K  mark. I just want to ask if my assumption is correct,<Yes> or if there are some special marine designed bulbs in the upper temperature range that have higher CRI values. <A color rendering index of 100 would be equivalent to high noon in the tropics, that is, the most natural color.  A lower CRI does not necessarily mean the light is no good for your corals as certain wavelengths filter out very quickly the deeper the light penetrates the water. These high temp bulbs at the proper wattage per gallon (4 to 8) provide enough intensity for the corals to live.  The higher temperature bulbs (10K+) are closer to the color you would actually see on the reef.  Hope this makes sense.  Just got back from the madhouse in Detroit and the mind is foggy.> I also read in one of your articles that unshielded bulbs can put out dangerous UV A, B,& C rays and must be filtered. Is a piece of glass placed on the output end of the fixture adequate to filter these harmful rays, or are there special lenses you need to get for filtering purposes. If you need special lenses do you know of any sources?  <Glass works, but acrylic is better, no special lenses needed.> Thank you for your help. <You're welcome, James (Salty Dog)> Brad

- Lighting For Corals - Hi! Just found your website a few days ago - Wow! I've never seen so much current and useful information on marine aquaria in one place. And the amount of time you guys spend answering questions and otherwise assisting fellow hobbyist is just incredible. You guys are terrific. About two years ago my daughters bought me a twelve gallon Eclipse tank, some marine salt, a little crushed coral and a yellow tail damsel for my birthday. Since then I've changed to a live sand bed, added lots live rock, a few fish and some low light (mushrooms, etc) corals. All are doing well. (oh, and I hear my daughters are okay too... I spend most of my time with my nose pressed against the glass of the aquarium...). I've got my eye on a 100 gallon acrylic tank and as soon as I can convince my wife we can't live without it (and I'm so close!!!), it's mine. Even though I'm still fairly new, I already know that water quality is number one. It's like the air we breathe. Can't go for long without good air and those guys can't make it for long without good water. But we're able to measure water quality right down to the millionth part per gal/ltr, so there's really no excuse for poor water quality. It seems another major issue and my concern/interest right now is lighting for the reef tank. All I ever see is "low, moderate and high". Just what the heck does that mean? <Pretty much exactly what it sounds like - depending on the animals you choose, the lighting will need to suit their needs. Of course, tank depth is also a variable, but for the most part low intensity lighting refers to normal output fluorescent lighting. Moderate intensity lighting refers to VHO or PC fluorescent lighting, and high intensity refers to metal halide lighting. Quantities and color temperatures will vary based on tank size and depth and also the age of your bulbs. Please read here: http://www.wetwebmedia.com/marine/setup/lighting/index.htm > It all seems so ambiguous in such a scientific age! I know there are all kinds of sophisticated scientific gadgets to measure light that are not available to the average hobbyist, but surely we can do better than "low, moderate and high". <Read on, you will see...> In the things I have read, I have learned that at the surface of the water in the tropics, at noon on an average day, the sun provides about 100,000 lux of 5500K light. Within fifteen feet, the reds and oranges are absorbed and the lux are down to about 20,000. By thirty feet, the yellow light is gone and the lux have dropped to 10,000....etc. <Well... you realize that no amount of mechanical lighting will ever equal the output of the sun, and likewise very few people have 30 foot deep tanks.> Okay, finally, here's my question! Has anyone gone to the trouble of making up a simple chart for salt water aquarist that would show this progression of light reduction and Kelvin temperature change as the depth increases? <Not that I am aware of, but still... the amount of light you choose to use is dependent on the animals you choose to keep - Tridacnid clams for instance must have metal halide lighting or they will not thrive. Fish on the other hand, don't require this type of high-intensity lighting... so, is your budget for your electric bill unlimited? If so, light fish with any lighting you choose - for the rest of us, there are offsetting choices that must be balanced between the acquisition/operating costs of a particular type of lighting and the animals we want to keep.> I know there are variables such as water clarity, etc., but a general chart could be developed... and here's the payoff. By identifying the various corals at the depth in which they are usually found, it would be possible to much more clearly identify their light needs - or at least the range of lighting conditions in which they are most likely to flourish. <Essentially, this much has already been determined, and again low, moderate, and high does suit the bill.> Sure, it might mean I'd want to go buy a $100 light meter, but I'd rather do that than guess whether my corals are getting enough (or too much) light, or whether I need to move one of them to a healthier location in the tank. <Do you have a specific animal and tank size in mind here? That might help answer your questions - or as you mentioned, to satisfy your own curiosities, you might just want to track down and purchase a lux meter.> Maybe such a chart or publication already exists, or maybe - being new to this hobby - I've overlooked or over-simplified something that would not make this idea practical, but it just seems we can do better for our little critters than "low, moderate, high". <Not sure we'll agree on this, but it's been working well for a while now.> Your advise/comments would be appreciated. Thanks. Rick Venice, Fl <Cheers, J -- > 

Lighting for corals Hi Bob (and all the other good folks!) With your advice and some wonderful references, I now have two thriving reef aquariums- one 55g and one 10g which is a constant source of amazement- it is literally TEEMING with life forms, with new creatures being discovered daily. <awesome to hear!> With this success behind me (wink), I am considering moving on to corals (in the big tank, although it looks like a tree-like coral is growing in the small tank). Having read most of the literature on lighting, I am confused on some things. 1) Light is preferred at 1-2 watts/gallon, so it seems, yet much of what I read would indicate double that requirement- is more better? I don't want to burn them... <the watts per gallon rule is complete bunk. I explain it and likely most of what you are wondering here: http://www.wetwebmedia.com/marlgtganthony.htm do follow up with questions if necessary> 2) Metal Halides seem to be preferred, yet one source states they are unnecessary if the water is less than 18"  <agreed essentially> and another source claims they need remain on no longer than 2-4 hours daily... <disagree here... MH lamps are ideal lights for tanks over 24" deep and they are in fact the most economical light (bang for your buck). Shallow tanks simply may not need them and no discussion of water depth is relevant without first identifying the corals that will be kept. We must ID our corals on a guest list or wish list before we can buy lights to suit their needs. Do your self a favor and try to stay with one main group of corals and not mix a little of everything. There are many complications with the typical mixed garden reef that has LPS, SPS, soft corals, Zoantharians, etc all mixed together. Stick with Soft corals only most likely> if I keep soft corals, within 6" of the water surface, do I require them? I have 1 actinic 40w bulb, 1 daylight (10,000k ?) 40w, and two 15w standard aquarium fluorescents- 110w total. <2 175-watt 10K Aqualine MH lamps would be ideal IMO if you like higher light animals (colored leathers, clams, sps). Or, if you stick with hardier medium light animals... 4-6 110watt VHO bulbs will serve you well> Once again, effusive praise and accolades...but seriously, I DO appreciate both your wisdom and your timeliness on responding- I could not have made the 55g a success, let alone the 10g, without your guidance- that goes for the whole team. Gerry Sames <wishing you the best! Anthony>

Coral Lighting Bob, Great site.  <thanks kindly> I have a 75g tank (48x19x20) currently with an Ice cap system. 1-Actinic blue and 2-actinic daylights (46.5" 110 watt bulbs).  <still... corals must be kept in top 10-12 " for best health> I have about 60# of Fiji rock and about to add 20# more prior to adding coral. Is this lighting adequate? I was thinking of adding one more bulb possibly the URI actinic sun. What do you think? Is more better? <to some extent... but it still doesn't change the fact that fluorescents do not penetrate very deep... no matter how many lamps are above. See here for more information: http://www.wetwebmedia.com/marlgtganthony.htm > thanks DJ<best regards, Anthony>

Small Marine Aquariums
Book 1: Invertebrates, Algae
New Print and eBook on Amazon:
by Robert (Bob) Fenner
Small Marine Aquariums
ook 2: Fishes
New Print and eBook on Amazon: by Robert (Bob) Fenner
Small Marine Aquariums Book 3: Systems
New Print and eBook on Amazon:
by Robert (Bob) Fenner
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