Claire Corlett

Fish Food, Fish Tanks, and More
The Deep Dive into Reef Aquarium Lighting

The Deep Dive into Reef Aquarium Lighting


Every now and again I like to cover a larger
topic in the hobby and lighting in particular is a loaded topic. Last week I did a short video on just how
much of an effect our choice of lighting makes aesthetically and in the comments people overwhelmingly
asked for a deeper dive into the topic of lighting. Let’s start with some basics and then work
our way to the different types of fixtures. Grab your favorite beverage because this one
might take a while. Lighting is important because it directly
affects how we visually enjoy the hobby and the vast majority of the corals in our tanks
are photosynthetic. Coral as we know it are a symbiotic relationship
between the actual coral animal and dinoflagellates called zooxanthellae. Zooxanthellae live in the tissue of the coral
and are like algae in that they contain chlorophyll for photosynthesis. The byproducts of photosynthesis are things
like simple sugars that the coral hosts can then use as an energy source. The color of zooxanthellae is varying degrees
of brown, but there are over 80 known varieties of zooxanthellae which can give coral a different
look. Corals occasionally expel zooxanthellae to
control both the amount of dinoflagellates and the varieties residing in its tissue. This is easiest to see in LPS where one might
see brown stringy material getting spit out. This is usually done to adjust for some change
in the environment or a stress reaction. The color of light is important not only for
aesthetics but for the photosynthetic process. Chlorophyll in zooxanthellae does not absorb
light uniformly. There are certain spectrums of light that
are absorbed highly and other spectrums that are rejected. The type of chlorophyll most commonly found
in corals is Chlorophyll A and it has two major absorption peaks. One at the 440 nm wavelength which is a violet
light and the other at the 675nm wavelength which is a red light. Light spectrums neighboring those spectral
peaks are also absorbed by Chlorophyll A but also by different compounds such as Chlorophyll
C and carotenoids so it is important for whatever lighting you choose to have a robust spectrum
outside of just the 675nm and 440nm spectral peaks. The color of light is measured by a Kelvin
rating. If you recall from high school physics and
chemistry Kelvins is basically Celsius but starts at absolute zero rather than the freezing
point of water. So zero degrees Kelvin is equivalent to -273.15
degrees Celsius. Anyhow, once you start turning up the temperature,
this theoretical black body starts to emit light. The best way to visualize this is to imagine
a star. Our sun burns at just under 6,000K and we
get that yellow light as a result. Once you get to about 8,000K to 10,000K in
temperature the black body radiates white light. Between 15,000K to 25,000K the radiation appears
blue. So just to clarify, the bulbs in your tank
that are 10,000K are not burning at that temperature they are just a similar color as a star that
is actually burning that hot. A common misconception about higher Kelvin
light bulbs is that they don’t necessarily have more blue than lower Kelvin bulbs that
appear more yellow. The blue light in these bulbs is achieved
by reducing the red, green, and yellow phosphors. It’s entirely possible for a 6,500K yellow
looking bulb to have a great deal more blue spectrum available for photosynthesis than
a 20,000K bulb. Still, there are perks to using higher Kelvin
bulbs. Bluer light is aesthetically pleasing but
has the side perk of algae control as algae tends to rely more on the reds, yellows, and
greens compared to coral. Having said that, lower K bulbs grow coral
faster. Possibly the best bulb I have ever seen at
growing corals was the 6500K Iwasaki although it was arguably the least attractive color
unless you are looking for a very yellow-looking shallow water reef. When I started into reef keeping, the rule
was get the brightest lighting possible. End of story. The most I have ever had on a tank was two
400W metal halides, and four 110W VHO fluorescents over a 75 gallon tank. Needless to say it was bright and warm. Fast forward about 20-something years and
I have some corals in extremely dimly lit tanks doing just fine. So in the bright tank example the intensity
was probably close to 1200 PAR if not more. In my low light setup, the PAR was about 50. In both cases, coral grew just fine. In fact, with the exception of Acropora the
vast majority of the corals we keep here do quite well in low light. What seems to be more important than raw intensity
is consistency. I get asked fairly often what light is the
best light. Unfortunately there is no right answer. First off, there is the difference in aesthetics. That is a purely subjective decision that
only the hobbyist can make for themselves. In terms of coral biology, what type of lighting
that will work the best for your tank will depend a great deal on what animals you intend
to keep. As I mentioned before, corals will adapt to
lighting by regulating their zooxanthellae so most coral will grow under any of these
lighting technologies. Having said that, it is also entirely possible
to have some corals take on a desirable appearance while other corals become less attractive
under the same light. As far as the type of technology to use, it
will depend on what aspects of the technology are most important to you. There are also pros and cons to any type of
lighting technology whether it is LED, T5, metal halide, or even natural sunlight. Depending on your situation, the drawbacks
of one technology might not matter to you. Conversely, the benefits of another technology
might not be meaningful to you. Let’s talk for a bit about each one in turn,
starting with the most popular. LED fixtures are nice because they are offer
the most in terms of control. It is possible to control each LED individually,
so the hobbyist can customize the schedule, colors, and intensity. Of all the types of lighting I think LEDs
do the best job of showcasing corals by bringing out the most appealing fluorescence. They are energy efficient and the LED’s
themselves are long-lasting. Lastly, the fixtures tend to run cooler than
T5 fluorescents or metal halides which is a big deal for hobbyists in warmer climates
that have to battle to cool their tanks. It is far more difficult to cool water down
than it is to heat it up. The downside to LED’s is that some corals
do not color up as well under LED as they would under other types of light, in particular
SPS and certain LPS such as Acanthastrea and Micromussa. I use a lot of LED in my greenhouse currently
mainly to conserve energy, but I prefer both T5 and metal halide when it comes to growth
developing color. Some aquarists have issues with the spotlight
nature of LED’s where dark shadow areas on the underside of corals cause the colony
to die off. Also, while the LED’s last a long time,
the longevity of the fixture can be substantially shorter than the rated life of the LED because
other electronic components fail. The last downside to LED is not going to affect
too many people, but for those interested in photography, LED is the worst light ever
invented. For better or worse, LED are quickly becoming
the most popular form of lighting in the hobby if it isn’t already. Compared to the other types it is the newest
technology and could see some major improvements down the line that eliminate many of the drawbacks
I listed. T5 Fluorescent bulbs are thin glass tubes
that produce a very robust light spectrum that colors up corals nicely. Almost every insanely colored SPS aquarium
that simply blew me away implemented this type of lighting. There are a lot of bulb choices available
which can give your tank pretty much any type of aesthetic. I say pretty much because the neon disco look
that an all blue LED light gives is pretty unique. While they are not controllable to the extent
LEDs are, there are some fixtures out there that can dim T5 bulbs to give that dawn/dusk
lighting effect (though I don’t know if that reduces the life of the bulbs). Lastly, because the light emitted by a T5
bulb is spread out evenly over the length of the bulb, there is almost no trace of shadowing
effects that plague point source lighting. No lighting system is perfect however, and
T5 fixtures have their drawbacks. First off, the bulb life is frustratingly
short. They begin to erode both in terms of spectrum
and intensity right around 6 months and by 12 months, they are a drastically different
bulb. Here at the greenhouse I run them a lot longer
than that just because they are supplementing the sunlight we receive, but when I do finally
get around to swapping out the bulbs, the difference is staggering. The second downside is the energy efficiency
while not horrible on a per-bulb basis is not as good as the LED lights. Depending on the number of bulbs in the fixture,
it can get expensive to operate. For example, if you have an 8-bulb fixture,
the electrical consumption along with the cost of bulb replacements, might make for
the most expensive lighting upkeep out of all the technologies. Lastly, the bulbs themselves are fragile and
can easily break during shipping, especially when you consider the longer bulb lengths
of 48” and 60”. Finally we get to metal halide which I would
venture to guess is the least popular form of lighting at the hobbyist level and likely
the most popular lighting at the commercial level. The positive aspects of metal halide are its
intensity, spectrum, and longevity. When it comes to growing light loving corals,
I don’t think any other technology does it as well. Metal halide bulbs are a point light source
like LED’s but are even more concentrated. When shining down into the tank they create
a very pleasing shimmering effect which is almost absent under the diffuse light of a
T5 fluorescent bulb. Those shimmer lines closely replicate what
is seen in nature and there was a study done several years back that indicated corals actually
benefitted from them. The major problem with metal halide is energy
consumption and heat. Metal halide bulbs consume a ton of electricity
and it will be noticeable on your monthly electric bill if you just installed a new
halide fixture. The heat generated by metal halides is also
something that had to be dealt with. In large aquariums situated in a large room,
some well-placed cooling fans might do the trick. On smaller aquariums or in tight quarters
where heat builds up, one might need to install a chiller or crank up the air conditioning
to compensate. Either way, heat management will further increase
the electricity bill. In terms of controllability, it is practically
absent from these bulbs. They can turn on and off. In some ways, they don’t even do that well
all the time because some require a cooling off period before being able to turn back
on. There are dimmable metal halides, but from
everything I’ve read it’s not great for the bulbs and some bulbs will shift colors
as a result. Now that we have gone over the types of lighting
hopefully you can see that all of them have their pros and cons. What will make for the best light in your
tank will depend in large part on the factors that are important to you. I can say up front that most corals can be
kept under just about any kind of light fixture. The list of corals that demand extremely intense
light is surprisingly short but who am I kidding, we aquarists are trying to squeeze out that
last 1% of color from our corals. Picking what light to go with can be daunting
but the obvious solution to deciding on a fixture is to not really decide on anything. You could get a light that incorporates more
than one tech. Hybrid lighting systems exist that combine
either LED and T5 or metal halide and T5 or metal halide and LED. There might even be some systems out there
that is a combination of all three, I don’t know. So if you really need the best of all worlds,
I’m sure there is a fixture out there for you. That fixture might shockingly expensive so
I can give you a cost saving tip. Let’s say you have some LED fixture you
are happy with but want to supplement it with T5, but you don’t like the look of the T5
bulbs. What you could do is purchase an inexpensive
T5 fixture with all white bulbs and only run it for about 4-6 hours while you are away
from the tank. That way, the corals still benefit from the
light and color up nicely but it doesn’t interfere with the aesthetic of the LEDs when
you return home. Tidal Gardens uses a mix of natural light
from a greenhouse structure and supplemental light from mainly T5 and LED fixtures. The idea when the greenhouse was constructed
back in 2002 was that the sun is the perfect light on the perfect timer and corals grown
under this light would be the healthiest specimens for lowest electrical cost. This premise still might be true, but not
necessarily in Ohio here where the greenhouse is located. The difference in lighting from season to
season has a drastic affect on the corals and some species don’t like it at all. One might guess that it is the cold dark Ohio
winters that are the problem, but it is actually the summers. The winter months it turns out are some of
the best for growing just about every coral. If I had to guess it has to do with both the
change in light intensity as well as the photo period. In the summer it feels like the sun is in
the sky twice as long and that is not a good thing. The shorter photoperiod of the winter months
has proven to be a much better situation for the corals here. Setups that are designed to use natural light
would be the most successful in areas that have the most consistent climates, but preferably
not in crazy hot climates because it is far more difficult to chill water than it is to
heat it up. So that does it for lighting. Clear as mud, right? Hopefully it helps you decide on what type
of lighting you want over your reef. If you like this kind of content give this
video a like. It helps me figure out the sorts of things
my viewers are interested in. Thanks for watching!

20 comments on “The Deep Dive into Reef Aquarium Lighting

  1. Kessil lighting is beautiful but there very bright I started my intensity at 50% and leached my sps coral I had to drop it to 30percent

  2. Love all your videos I especially like the dep fit you go into I even like your music and the tone of your voice lol it's always just such a joy to listen to you and watch what you have to show keep them coming sincere thanks

  3. I wish i had a guy like this as an older bro sometimes. I feel like having a mentor in the hobby would be a great thing. especially in the beginning. I find myself trying to cram in all this knowledge that truly takes years and personal experience to grasp completely. To all of those out there that are mentors, yall do mean a lot, whether its on youtube, a forum, facebook group, or a family member.

  4. Love your videos! Can you please do one that explains watts vs spectrum… I'm new to reefing and in my research, I'm finding somewhat conflicting information. I constantly hear the common watts per gallon advice but also hear about how spectrum is so important. Also, it seams like you can have too much light and "burn" or "bleach" corals? What's more important to coral health? I'm currently searching for my very first lighting system.

  5. I am thinking about entering the saltwater area, I have the perfect room for a Tank (I think so lol) one wall that faces east is all glass it is 10 feet high and 9 feet wide, and in the morning for about 4 hours this room is full of direct sunlight, That it would be a good place for the aquarium, about 350 gallons, of course I would not rely only on the sun, I would use LED lighting, and T5

  6. how has that tank in the begining of the video not broken?? lol theres big bumps and gaps under it  :O awesome informative video though

  7. Can you compare a few popular lights to a tank in the window, I want to build my first saltwater tank soon.

    And I don't know if I want to get a 10 to 30 g tank, or if I want to use my spare 55g, and I don't really want to spend, like $400+ upfront.

    And seeing people who do basic saltwater tanks for under $100, I'm wondering what's right for my first experience with salt water

  8. I like the look of a shallow water reef tank, as in a not so much blue. I get it's not best for growth but I'm assuming I could use both. I think the flourecence is cool but I like to imagine myself suba diving in the shallows. Any advice on what light?

  9. Need your expertise: I'm in the process to set a small 55 gal tank, planning to keep just acropora and montiporas. I have bought two kissell blue tuna 360NE . What's a recommended height above surface and would you mind to suggest some settings? I'll really appreciate your comments.

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