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Reef Tank Lighting Coverage & Shading
Last updated on May 7th, 2024
Reef Tank Lighting Made Easy
One of the most difficult topics in Reef Keeping and Coral Care is lighting. If it wasn't obvious enough from the number of videos and products on the market, I've even made a number of articles covering reef tank lighting. This concern usually comes from starting a new tank or just getting started with SPS, Acropora, or even high end LPS coral.
More often than most will admit, they buy a coral and put it in their tank thinking that their current lighting is enough. The problem is that for many beginners, they are using one or two small lights. Often the chinese black box lights from Ebay. Though these lights may have worked well for quite a while, the reality is that these are not designed for high end coral. There are a handful of people that grow coral under these lights, but what if I told you there was an easier way?
Reef Tank Light Coverage - PAR
PAR, or Photosynthetic Active Radiation is the amount of light available within the spectrum coral requires to grow. Each type of coral requires a different PAR value in order to grow effectively. For example, soft coral grows in very low PAR, where Acropora requires extraordinarily high PAR.
As a helping hand, here is a quick cheat sheet for approximating how much PAR is needed for the different coral types. Please keep in mind, these values are approximate and can vary between specific corals as well as tank parameters.
| Coral Type | Aprox. PAR Needs |
| Soft Coral (Zoas, Mushrooms, Leathers, etc.) | 50 - 150 |
| LPS Coral (Hammers, Torches, Acans, Duncans, etc.) | 50 - 150 |
| SPS Coral (Montipora, Milipora, etc.) | 200 - 500 (most around 300) |
| Acropora Coral | 300 - 500 (Varies by coral) |
There are a number of ways to dial in the correct PAR values. Some more scientifically accurate than others. The most accurate way to dial in a specific PAR value is to purchase an Apogee MQ-510 PAR Meter. This will let you measure the exact strength of the light in different areas of the reef tank, adjust your lighting to the desired values, and place coral accordingly.
The alternative is to set up lighting and place the highest demand coral at the top. Then adjust the lighting to ensure those coral are happy. Then move other coral up and down in the tank until they are happy. This is not as bad of a method as it sounds, mostly because each coral will need a slightly different value depending on flow and other parameters.
The ideal method, in my opinion, is a combination of the two. Measuring and knowing the PAR in various locations in your reef tank will allow you to pick ideal locations for different types of coral. Then, knowing the approximate PAR value of that location, you can move coral up or down as needed.
Why do we care about PAR for Coverage?
Why do we care about PAR for Reef Tank Light Coverage? Because even if there is light across the entire tank, the PAR in some areas may not be enough for some coral. This can come from poor light coverage and/or shading.
What is Reef Tank Lighting Coverage
Reef light coverage is ensuring the reef tank light covers all of the coral, and generally the aquascape. By ensuring the entire aquascape is wrapped in light, you can guarantee that any coral placed on the aquascape will be wrapped in light. Giving this coral the best chance to grow and thrive!
More than that, as the coral grows, it will become harder to illuminate the entire colonies. Wrapping corals in light will ensure the top half of these colonies have the light they need. The bottom of these coral colonies will generally gather light reflected off the glass walls of the reef tank as well as the sand or bottom glass. This aquarium light cannot reflect like this, however, unless the light coverage is wide enough to reflect this way.
So how do you know that you have appropriate coverage? The easiest way is just by looking at the coral and you can see if the coral is illuminated around the entire colony. This method is usually enough. However, it is not exactly scientific.
If you're trying to get exact PAR numbers to ensure that the coral has appropriate coverage, as well as making sure you have adequate lighting around the entire aquascape, you will need an Apogee MQ-510 PAR Meter. This way you can check that the PAR is high enough in all of the locations across your tank to ensure that you can grow coral anywhere.
Reef Tank Light Coverage Solutions
When deciding which reef tank lights you need to decide how much coverage and PAR you're looking to achieve. If you are keeping soft corals and LPS coral, you do not need to worry as much about reef tank light coverage and PAR as you would if you were keeping large SPS colonies.
You may want to consider coverage if you have large corals that shade themselves or other coral. In these cases, for soft and LPS coral, it may make more sense to add fill lighting than to double your main light fixtures. For large coral that demands more light, like acropora or other SPS coral, you may be interested in increasing your high-end reef lights. This allows for wall-to-wall SPS corals to grow and minimize shading!
See the below infographic about the different way to light a reef tank and the coverage you can expect. This infographic shows some options on how to light a 4 foot tank. By looking at the center brace, you can see ideas for what to do every 2 feet. Helping you decide on lighting for 2, 4, 6 and 8 foot long reef tanks.
Reef Tank Lighting - Shading
Reef Tank Light Coverage tends to deal with providing top-down lighting. The other thing to consider is coral and rocks shading. Shading occurs when rocks and coral block light from reaching other areas of the tank. When you have few light sources, there is little you can do to prevent shading.
You'll find that many of the same solutions to coverage apply to shading. The first solution is to add more sources of light. The light overlaps and comes from more angles due to the larger number of light sources. This provides adequate PAR and light coverage, while preventing shading.
Another solution is provide a larger light source above the tank. Using larger light fixtures, that are larger than the rockwork, does the same thing as providing more sources of light. Letting the light come from more area and bounce off the glass is another way to provide coverage and par while preventing shading.
Reef Tank Lighting Solutions
Reef Stable now offers a Reef Tank Store where I can provide easy solutions for you, and you are able to support the Blog! The prices are the same as buying the product from other large retailers, while supporting small business and allowing me to keep writing content for you!
My goal is to provide solutions for you in an easy way! Taking the guess work out of keeping a successful reef tank!
Large Fixture Lighting Solutions
If you are looking to light your reef by utilizing large panels that are bigger than the rock work, this is what I recommend.
Orphek Atlantik Reef Aquarium LED lighting
Orphek Atlantik is one of the larger form factor lights with some of the strongest LEDs available. It is controllable via an app and is honestly one of the best lights in terms of strength and coverage in my opinion.
Fill Light Bars
Finally, if you are using "Standard" or "Slightly More Lighting" options and want to solve coverage and shading problems, a popular and simple solution is to add fill light bars! The Orphek OR3 Bars, especially the Blue Plus Bars, are a favorite for MANY Reefers!
Conclusion
The intention to this article is to provide both information about the importance of reef tank lighting coverage, as well as simple solutions to solve them. Providing sufficient PAR across the entire tank lets you grow coral in more places, as well as allowing your reef to grow larger before the coral starts to die off due to lack of light. These solutions are intended to help you keep a beautiful reef with ease!
Hopefully you found something helpful in this article! If so, please share it with others using the links below!
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About the Author
John Krenzer
John is a Software Engineer with a passion for saltwater aquariums, as well as the founder and president of Reef Stable. He started in the aquarium hobby as a child with a 20 gallon freshwater aquarium. His interest in aquarium life grew and in 2008, John set up his first saltwater aquarium.
Today, John maintains an over 300 gallon reef tank system, consisting of a 120g reef and a 210g reef. These large tanks are contained within the same system, sharing a sump as a means to reduce total maintenance and increase total water volume.
John writes articles for the blog as a means to learn about more reef aquarium topics. These articles act as a reference for the readers as well as himself. John updates these articles frequently to provide additional information or make corrections as new information becomes available.
If you would like to request an article, tank tour article, or to collaborate, let me know via the Contact Me Page!
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