Aquarium Lighting

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Aug 24, 2015
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Aquarium Lighting

One of the hardest concepts to grasp is Lighting. It is also one of the most controversial topics brought up when talking to owners of pet stores and even veteran reefers. Try telling someone with 10 year old corals raised by fluorescent lighting that they need to upgrade to LED and they will say otherwise. This is not wrong if they are successful with their corals but why not upgrade when there are so many benefits? Sometimes it is just because they have not learned much about them.

Types of Lighting

The world is full of engineers that are capable of tinkering with data to the point where they can create nearly any color, shape, and wattage imaginable. Figuring out the one that is for you is tricky at first. To start off, there are many types of lights that require specific ballasts to power them. Some ballasts are designed to be somewhat interchangeable but the general population of light fixtures are only designed to support the one type of bulb they are made with. You cannot power a 40 watt CFL in a 400W metal halide fixture. It may cause an explosion, so please MATCH BALLASTS WITH THE APPROPRIATE BULBS! OR ELSE!

There are 3 types of lighting requirements. This includes Reef Lighting, Plant Lighting, and Non Photosynthetic Lighting. First you must know what kind you are growing, if anything.

For Non Photosynthetic Aquariums:

These are tanks with no need for lights beyond visibility purposes, the only thing to consider is what spectrum the particular algae for your type of water grows at and avoid it at all costs. Do not put a plant light on a tank with no plants, however the algae may benefit vegetarian animals you may plan to keep.


Planted Tanks and Refugium Lighting:

This type is designed to mimic natural sun lighting at shallow depths. Look at a pond, river, lake, or even the ocean. The shore and surface water grow much more plant life than depths at reef level. Often, the same spectrum can be used for refugiums, granted they are plant based and not for coral.


Image via Philippe Grosjean

Reef Lighting:

Freshwater has much fewer salt particles than salt water at a molecular level: DUH! But what does that mean? Think about a salt particle like a diamond. It refracts light in various ways. If you look at The cover of Pink Floyd’s Album, Dark Side of the Moon, you can see how white light can essentially split into various colors. Think about Kelvin like a color wheel or ROY G. BIV. Blue is the particular color you see at these depths due to the refraction filtering out all the other colors as you get deeper and deeper. But blue is not all that is there, that is just how we perceive it.


Mike&Terry’s 300G Reef

Oh No More Lighting?

How do we know what color we want for what? Luckily, most bulbs specify if they are for plants, reefs, or non-photosynthetic beings. To determine for yourself you must first understand Kelvin. This is the degree of color temperature. For example, (Thanks Wikipedia): The photosphere of the Sun, for instance, has an effective temperature of 5778 K! As Light makes it from the sun to the ocean floor the color temperature, or K, goes up. A zero K bulb would be considered OFF, since zero K means Zero Light.

Coral Farms that specialize in speed growing use 6500K Lighting, which does not give the corals the visual pleasure you see in people’s aquariums. It does produce growth better than any other color temperature. This is also a spectrum that works great for aquatic plants. Naturally brownish pink corals often thrive in this Shallow Spectrum. Places that farm corals cannot make money off browned out corals, so the 6500K is restricted to mother colonies and healing frags while giving them a boost until they are ready to be placed under different lighting. So “plant” lights are best kept on plants for visual pleasure. Here is a good discussion on refugium lighting: Refugium Lighting

We will be diving down to the 10,000K range. Here the light spectrum has a whiter appearance due to the mixture of colors left over from the refraction in the water. This produces more fluorescent appearance while still producing decent growth. Most stock Light fixtures will come with this spectrum. Here is a good color example of 10,000K lighting: 10,000K Lighting

If you don’t mind slower growth but want extreme coloration than move deeper into the reef. Here is where the light is 20,000K and the purple starts to be much more visible along with a deeper blue. This is as close nature will get you to a Black Light effect. In fact, having a reef tank with this color lighting makes things outside the tank glow just like a black light. The corals will develop insane colors and the tank will always look amazing. See for yourself! SPS Addiction

We’re Not Done Yet!

Color is important, but you cannot just throw a tiny 20,000K bulb over a public aquarium and feel good about yourself. The visibility of a light does not mean it is necessarily up to PAR. Put down your golf clubs, I am talking about photosynthetically active radiation. To measure this number, you can use a PAR meter. In Layman’s terms it is how much usable light is at a given point. Each coral comes from somewhere in nature. It is best to learn where and match the light intensity to that particular habitat. A High Light anemone will die if kept in a Low Light aquarium. On average, Reefers aim for 75-200 PAR in there tanks. Reef Lighting is a vague subject and extra attention must be paid to endure the health of your animals. Another measurement is the LUX reading which measures how many lumens are present per square inch. This helps when determining how bright the light will actually be at certain distances from the bulb. Unlike color temp, this can be manipulated simply by raising or lowering the wattage used or raising or lowering the fixture itself if possible. A 400w metal halide can support a 10 gallon tank just fine if it is held up high enough, but we would never recommend that.

3-10 watts per gallon is what the old “rule of thumb” states, but that could be the difference between 300-1000 watts and anything in between for a little 100 gallon tank. The only way to properly know what you really need as far as wattage is in fact a PAR meter or someone who has already tested for PAR in a tank as close to yours as possible. Manufactures tend to exaggerate on their products sometimes, so pay attention to reviews and what experienced people have used. BULBS MATTER. BALLASTS MATTER. REFLECTORS MATTER. You get what you pay for most of the time. Do not skimp on what is only 2nd in importance to H20 itself.

More Information?! COME ON!

Now that you are a theoretical light genius, it is time to discuss the various types of bulbs. Again, the bulbs and ballasts must be compatible. READ THE MANUALS!

Florescent Lighting Comes in various sizes. The Tube Shaped bulbs are classified as normal output (NO), or very high output (VHO) Normal output are what you see on regular freshwater aquariums or in homes and buildings. VHO bulbs are, (very) roughly, three times as powerful. They are much more useful in reef applications.


Power Compact- These bulbs are what they say, powerful and compact. A 55w PC bulb is much smaller than even a 40W florescent. They are double tube shaped and can have various connections.


T5HO-T5 High Output bulbs are extremely popular. They are very thin, which means an individual bulb can have its own reflector and take up the same space as its grandpa VHO. They come in an extreme array of colors. Some brands can even be over driven, meaning even more light than they are advertised.


Metal Halide- One of the hottest, brightest bulbs on the market. A 400 watt metal halide can cook you dinner if it does not explode from you touching it first. These are the lights you saw sparkling before LED came into the picture. Replicating the sun itself, these are some heavy duty bulbs that can be as large as your head or as small as your bottle of Mini M&Ms. 150 watts can be backed down into a 3 inch stick of a bulb that fits in the palm of your hand. They penetrate deeper than any equal wattage florescent.


LED- Not Zeppelin. Light Emitting Diodes are the newest trend. Originally as dull as Christmas tree lights, these little specks of light have evolved into beams beyond our dreams. One 3W cree Led of the correct color spectrum can shine straight down through 12 feet of water and see the bottom clearly. A group o them can support even the most demanding of Photosynthetic animals. These little dots of power are slowly putting halides on the old equipment list. Advancements have made them affordable and the best 2 things a light could offer are available with LED. LOW HEAT and LONGEVITY. All bulbs mentioned above need replaced around 4-8 months depending on usage. LEDS can last up to 10 years without loosing their color! And when they go bad they are cheap to replace with a little soldering skill.


Natural Sun- When choosing the sun, remember what you learned about spectrum. The color range of your aquarium will be yellowy in comparison to the standard blue/white look. Some may prefer actinic supplemental lighting. A strip of blue LEDs accent very well. All it takes is a little experimentation to find your desired result.

There are other types of lights as well, but the ones mentioned above are the most popular and successful. Any and all of the above lights can be used together. LED/HALIDE combo, NATURAL SUN/T5HO combo…the list goes on and on and on and ALRIGHT ALREADY!

When choosing lights, think about what corals you may want. Think about how flexible the lights you are considering can be if you change your mind along the way. And lastly, think about what you can or cannot afford or build. Often times the DIY way is cheaper, but requires knowledge of electricity. Don’t be afraid to ask someone who has experience with your particular situation, like all aspects of the hobby: Someone has been there and done that.

SCHEDULE: This is fairly flexible, as each light produces a different amount of photosynthetic activity. If you have 1000 watts on a 75 gallon you will not need the lights on as long as if you were only using 500 watts. If you have your tank in a room with no sunlight like a good reefer, you can have your photo-period any time that suits you, even at night time! Photo-Period

So how many hours a day should you illuminate your reef? 8 hours is the average, but the time can range from 3 hours to 16 hours in extreme situations. The single most effective way to learn what your tank loves is to simply experiment and ask fellow reefers with similar setups how they have their lights on. I can say you should keep you lights on for 12 hours a day but I have LEDs. 12 Hours of metal halide could potentially bleach your corals so BEWARE!!! Your aquarium is essentially the equivalent of a tanning bed, do your best to not burn your tank!

For more information on spectrum here is a great article! Light Spectrum

Is it HARD or EASY for you to keep your corals colorful? (check all that apply)

  • SPS Hard

    Votes: 225 61.6%
  • SPS Easy

    Votes: 87 23.8%
  • LPS Hard

    Votes: 57 15.6%
  • LPS Easy

    Votes: 234 64.1%
  • Zoas Hard

    Votes: 39 10.7%
  • Zoas Easy

    Votes: 227 62.2%
  • Soft Corals Hard

    Votes: 33 9.0%
  • Soft Corals Easy

    Votes: 238 65.2%

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