Saltwater Aquarium Lighting Guide (Beginner FAQ)

Image Credit: Reef Tank Resource
Image Credit: Reef Tank Resource

Saltwater Aquarium Lighting Guide (Beginner FAQ)


Reef tanks have a lot of factors that need to be taken into consideration for them to be at their best. From the filtration and dimensions to the reef tank’s inhabitants and plants, every decision that is made will have an impact on the system in one way or another. That is just as true for the reef aquarium lights that you choose to illuminate your fish aquarium with. Reef lighting is incredibly important for aquatic life for a multitude of reasons, so it’s important to begin to gain an understanding of the different elements that go into planning a lighting system for your reef aquarium.

From LED light to fluorescent lights, it can be overwhelming initially when you begin to consider everything that goes into selecting a reef aquarium light. However, just continue reading this saltwater aquarium lighting guide, and you should begin to develop the mindset for accurately selecting your lighting system.

Best Reef Tank Lights

Kessil A360X

Kessil is my personal choice. They take the guesswork out of lighting.

AI Prime 16

Incredible and popular budget light with loads of options for control.

RedSea ReefLED 50

A new solution from the RedSea powerhouse that rivals lights from Kessil.

Radion XR15 G5


Excellent light from high-end brand EcoTech that is highly configurable.

Lighting is about more than the appearance

A common misconception is that light is just how bright or dark your reef tank is, but that is only a small part of the job of aquarium lights. Saltwater aquarium lighting affects the overall health of your tank’s ecosystem. For those of us who are retaining our grade school science lessons, the plants in your reef tank will require some light to thrive due to photosynthesis.

Your plants will use this light to create food for themselves, but your plants aren’t the only organisms who use this process in your reef tank. The Zooxanthellae that grow inside coral require sunlight to thrive and since they need sunlight to thrive, so do your coral. The Zooxanthella in your saltwater aquarium provides food and oxygen to your corals.

Fish also benefit from the lighting in your reef tank as many are hardwired for the light levels to inform them when to be active or not. It will give them a sense of routine and can help with managing their behavior like encouraging mating.

Finally, you can also make your saltwater aquarium look really nice. Of course, you need to take into consideration the spectrum and light intensity needs of your reef aquarium, but as you learn to work within those parameters, you will also learn how to adjust the lighting for a really ascetically pleasing display.

What is the best lighting for a saltwater tank?

That’s the golden question, isn’t it? It would be great if there could just be a one-size-fits-all system, but that isn’t necessarily true. Reef tanks can be so different in their ecosystems and populations that you need to consider the needs of everything that you plan to incorporate into your system before you can begin to start buying new lighting. What creature are you planning on including? Are you considering introducing corals? If so, what kind of corals are you interested in including in your reef tank?

All of these choices will have a ripple effect on the needs of your reef tank. If you are planning your first saltwater aquarium, the best thing you might do is create a physical outline of the different species. Write down the names and specific needs of your planned inhabitants, including water parameters, behavior, and especially lighting. This step will help you to better identify the lighting setup that is best for you.

The lighting is, for the most part, one of the more adaptable pieces of equipment. Fish and coral have a range they can live within for their lighting needs, but they also won’t be in immediate danger if their lighting isn’t perfect right away. Monitoring your setup is one of the most important habits you can begin to practice. In fact, that same paper where you recorded your fish and coral needs? Use it to track their behavior over the course of a few months. This will allow you to make better judgments on where to adjust the parameters of your tank, including the lighting.

PAR vs. PUR in aquarium lights

There are a lot of terms used in lighting systems that don’t translate much to the rest of caring for aquatic life. That is to say, lighting is important, but it uses terms that you won’t find in other parts of the hobby. The PAR, for instance, is important to understand to better gauge the needs of your plants and corals in different areas of your tank. The PAR is essentially the light output energy of your light fixture.

Then you have your PUR, which is the useful energy or, in other words, the light output energy. These measurements will be important to gauge the proper levels for your tank’s inhabitants.

Types of saltwater aquarium lighting

There are a few different types of saltwater aquarium light setups that can be purchased. Despite what you might think, saltwater aquarium lighting is not all created equally. You might think that “light is light,” but it can make all the difference to your tank’s inhabitants. Taking the time to consider the nuances of the different lights will allow you to ensure that your fish and coral will thrive for years to come.

Saltwater aquarium LED light

LED lights are still relatively new to the hobby, but they have quickly become one of the most popular choices. Though they can be a little expensive compared to the more traditional lighting methods available on the market, LED lights can offer a host of benefits that you would be hard-pressed to find in most other lighting models. Most models will allow you to have a lot of control over the different intensities and color spectrum, which makes for a very adaptable system.

LED lighting fixture pros

    • Allow tighter control over the individual colors being produced
    • Greater adjustments over the strength of the lights
    • Low heat compared to other fixtures
    • The running cost is lower than most other models

LED lighting fixture cons

    • Can be pricier than other methods of lighting
    • Can be troublesome to find since they sell out quickly since they are still so new

Can you grow coral with LED lighting?

LED lights can definitely grow coral, but it is important to consider the intensity of the light that the coral will need to thrive. To learn more about how to tune your lights to adhere to the needs of your corals, see the section below about “adjusting lighting spectrum.”

Are LED lights bad for fish or coral?

Absolutely not. In fact, they have less of a chance to harm your fish and corals than a more traditional model. Traditional lights have the potential to run hot and affect the temperature of the tank, which your fish and corals will not appreciate. An LED light fixture doesn’t run hot like other lights, so it won’t affect the temperature levels of your tank. This makes it a much more manageable system, especially for newer hobbyists.

Saltwater aquarium T5 lighting

T5 aquarium lighting is so named due to the measurements of its tubes which are 5/8s inches. It is one of the more traditional fluorescent saltwater aquarium lighting systems and has been pinned down to a science for many reefers. T5 aquarium lighting can offer a great level of control over the light distribution in your tank, but the number of bulbs that it uses can affect the overall running cost in the long term. These were the go-to fixtures before LED began to step up the competition, but there is a reason for its longevity.

T5 lighting fixture pros

    • Produce more lumens than most other lighting fixtures
    • Lamps so powerful that only a few do the job of many
    • Different models offer a wide range of colors and intensities, allowing for more options and flexibility in your tank

T5 lighting fixture cons

    • Their energy savings have become obsolete compared to LED lights
    • Models do not always come with timers or other features and will require you to spend a little more money to compensate for the deficiency

But what about T8 lighting?

The difference between the T8 and T5 fixtures is the measurement of the diameter of their bulbs. The T5’s are much small light fixtures which you might not initially think is a good thing, but it is. The smaller size of the lights allows for more to be fit into space and produces better lighting overall. Plus, T5’s are just more powerful, so you get more bang for your buck.

Saltwater aquarium Metal Halide lighting

Metal Halide lighting is one of the most powerful lighting fixtures. They are high-intensity lighting systems, so they produce a lot of light, but it is also on par with LED lights but with a much higher running cost. The lights can burn so brightly because they use glass bulbs interconnected with wires running between them. When electricity is run through it, the metals and gases heat up to produce high-intensity light. They also can run really hot compared to the other light options. If cost savings is in your plan, then these lights might not be the best decision.

Metal Halide lighting fixture pros

    • Powerful light production up to 1000 watts
    • High-quality light

Metal Halide lighting fixture cons

    • Short lifespan
    • Can run very hot
    • Not as cost-effective as other lighting options
    • lack of proper adjustments and color options

Are T5 lights better than LED for a reef tank?

T5 lighting was once considered the gold standard in aquarium lighting until LEDs came along. Aquarium LED lighting has become stiff competition for the T5s but is there saltwater aquarium lighting that is truly better? That might depend more on your own preference than any objective points but let’s discuss some of the standout differences between the two types of aquarium lighting.

The most standout benefit of aquarium LED lighting over the traditional T5 saltwater aquarium lighting is the overall running cost. LEDs will require less power but will still provide a strong light intensity to your tank. However, the T5 lights can be tuned in whatever way you could imagine, but you will need to perform some manual labor and shell out a little extra cash to replace the bulbs. You arent going to be able to achieve the same level of tunability with the average LED lighting, but LEDs are still very customizable within their programming.

LEDs are a great choice for someone on a budget. They will provide a light intensity that can match the T5 fixture and adjust to a wide portion of the light spectrum. The best model of T5 can’t be beaten, though, but it is much more expensive and possibly not even worth the extra light control.

Are different light bulbs that important?

Traditionally, light bulbs have allowed people to light their tank exactly how they may choose. The bulbs provided a level of tuning that most closely matched the saltwater aquarium inhabitants’ natural habitat. However, bulbs are only for certain models of aquarium lighting like the T5, while aquarium LED doesn’t take different bulbs but can be adjusted within its programming. There are different bulbs for different tank setups. Here are just a few of the options you have to consider while you are planning your reef lighting.

  • Actinic white bulbs – Creates a white and blue light
  • Actinic bulbs – Emits a higher blue light
  • Plant bulbs – A bulb that focuses on plant growth by using red and blue light
  • Color enhancing bulbs – Designed to make fish colors pop while using colors from the warmer end of the spectrum

Generally, what you might consider proper lighting will depend on your specific setup and personal preference. The first thing to focus on is adhering to the needs of your fish, coral, and plants, but as long as those needs are met, feel free to make your tank shine anyway your can.

What is a light level, and how do I use it?

Some organisms in your tank, like plants, might come with a recommended light level. These levels are to better ensure that the plant will receive the energy it needs to survive, but what exactly do they mean, and how do you determine your light level?

Consider you are using T5 bulbs, you might have a low lighting range that uses about .25 watts per liter of water, or you might have a high lighting system by running .8 to 1 watt per liter of water. Knowing what might be considered low vs. high lighting and everything in between will help you to manage the needs of your plants. This is only one way to judge the lighting in your tank.

For reef LED light fixtures, there’s also a range that uses lumens per liter of water. The lumens are a measurement of how much light you are getting your saltwater aquarium light bulbs. You can measure lumens by using this calculator to determine what light intensity you might need. The corresponding range to the values that we previously listed should look something like this:

  • low lighting is 15 lumens
  • Medium lighting around 30 lumens
  • High lighting is 60 lumens


You should always review the manufacturer’s instructions as they will have insights into the total output of reef LED lights.

Knowing how to measure the specific light values of your lighting system will help you better prepare your tank’s parameters for your plants and coral.

But what light fixture is best for me?

You will have to ultimately make that decision for yourself because only you know the specific setup and needs of your tank. However, you shouldn’t feel like you are restricted to a single lighting system. You might even consider using a combination of systems, but this will more than likely be more expensive.

You could run your saltwater aquarium with a metal halide system and include T5 lighting too. This practice, when done properly, can allow you to have a saltwater aquarium that boosts plant and coral growth while giving an aesthetically pleasing display.

Ultimately, there is no one size fits all lighting system. There are so many different tank setups from the types of inhabitants, to plants, to corals, and even the dimensions of the tank that are trying to prescribe a universal lighting system are impractical.

What is the best light spectrum for coral growth?

The light spectrum that you set your light system to will have a lot more influence on the health of your tank than just how aesthetically pleasing it looks at different times of the day. Your coral will require a specific spectrum of light to thrive in the tank, and this is because light actually provides sustenance to the coral. Altering the spectrum to meet certain ascetic desires rather than the needs of the coral will result in unhealthy coral growth. Only a consistent spectrum of light will ensure that your corals reach peak health in your reef tank. So, what is the best spectrum for corals?

That depends on the type of coral you have, as different corals live in different depths of water, so the light that reaches them is different in their natural habitat. In general, the light wavelength should be around 370 to 500 nm, while the color spectrum should include the blues and violets. There will be differences depending on the type, but you probably will not need as much green and orange light.

The blue and violets on the spectrum will reach further into the depths of the water in your tank. A red wavelength might work well for more naturally shallow dwelling corals. Make sure to do the proper research as to where your coral is found in the wild. The most important responsibility of a hobbyist is to replicate the natural habitat of the organisms we are caring for in our reef tanks; that includes the corals.

In fact, greens, reds, and orange light should probably stay on the lower percentages. Aim for light on this part of the spectrum to be less than 20 percent. These colors are not really seen often in the coral’s natural habitat, and few corals will need them.

Remember, this is all in a very broad sense. We will cover some of the different types of corals below to get a better idea of the specific light requirements of the coral, but it is important to understand the ramifications of getting the saltwater aquarium lighting correct.

Use PAR to accurately measure your light

If you are setting up a new saltwater aquarium lighting system, it is always a good idea to get a PAR meter to measure the light in your tank. It will allow you to make accurate adjustments to your lights as needed too. If you don’t own one, you can always look to see if your local pet store (or an online retailer) has one available for rent. That way, you don’t need to drop too much money on a device that you usually only use when establishing your reef aquarium lighting.

Use the meter to measure the different areas in your tank that you plan to introduce coral or where you already have coral. The strength of the light will be different depending on the area of the tank your position it. That is due to both the light fixture’s settings and the water’s interference with the light.

Now for those of you who think they can just look at where the lights are reaching and adjust based on that, I urge you to reconsider. The light spectrum that we can register with our eyes is on a different level than that of the actual levels of light. The “real” aquarium lighting that you need to adjust for needs to be measured by a PAR meter or similar light intensity measuring device.

The only real change that you might be able to determine based on your level of experience is how well your corals and plants react to the aquarium lighting. For instance, if your saltwater aquarium lighting is too bright or the PAR measurement is way higher than it needs to be, then you might start to see your coral try to get away from the light by retracting. If that is the case, begin to lower your measurements on your reef aquarium lighting system.

How much light do soft corals need?

The optimal range of your light intensity for your soft and LPS corals will be much lower than that of your SPS corals. At only 75 – 150 PAR, soft corals do not need that much light compared to SPS corals which have a range of 200 – 500 PAR. Remember, how far on which side of the range can depend on the species of coral that you are caring for. Your corals will give you time to make the proper adjustments in lighting. You just need to be monitoring for any changes in your corals to see if the light isn’t appropriate in your reef aquarium.

Can a fish tank's light be too bright?

Yes, it can. While your plants, fish, and coral need quality saltwater aquarium lighting to thrive, having too much can result in some non-desirable consequences. Corals risk bleaching when they are exposed to a light intensity that is too strong for them. Bright lights can also affect the water temperature, which will disturb the well-being of your fish.

It isn’t just the light intensity that is important to consider for your tank; your reef tank needs a little darkness, too, just like the ocean. Try to aim for 12 hours of light for your tank, or you can match your own daily sleep schedule for a more consistent routine. You should also consider setting your light to a lower intensity and focusing on the blue spectrum for nighttime; think of it as a sleep mode. It will set the mood and also provide people the opportunity to see the tank late at night.

Do corals need light at night?

Coral growth happens mostly during the day since that is when the sun is at its strongest. The majority of the photosynthesis process happens then, so it isn’t necessary to have light during the night. You should have some sort of dim, low-intensity light and avoid complete darkness as it isn’t natural for corals. Dimming your reef aquarium lights at night will also help save you some money on your electricity bill. Some hobbyists shine just a little blue moonlight to make their corals fluoresce in the night. If you don’t think you can keep up with this practice yourself, then you can always invest in a timer for your aquarium light. A timer works just as you might expect. You set the timer for when the light should turn off and on, and the device handles the rest. A word of warning considering timers: there is the possibility that a timer can break. A lot of the cheaper models tend to do this, and it can cause issues for your entire system. Make it a habit to check your timer like you would any piece of equipment in your tank. That way, you won’t run into the issue where you think your lights are being turned off in your office aquarium, when in fact, they are left on all night.

What are reef tank moonlights used for?

Moonlights are an extra addition to your lighting system that aims to recreate the natural moonlight feel for your tank’s inhabitants. The benefits of doing so are both practical and aesthetically pleasing. Fish actually sync with the moon’s illumination; thus, the mating habits of some species can be facilitated by paying attention to the nighttime lighting.

Moonlights are also able to produce different light colors on the spectrum, which gives the hobbyist the ability to control what they are trying to do with their reef tank. For instance, if you are interested in making your corals fluoresce at night, then you would want to make sure the spectrum is veering more on the blue side. Though you should know that the natural spectrum for the night is often closer to red, although there doesn’t appear to be any harm in using blue light at night.

The units are also much more compact than they were when they were originally introduced to the market and come with a lot more options for controlling the light. For instance, many will come with an option that tries to copy the actual moon’s cycle so that your fish and plants will experience a more natural lighting cycle.

However, it is also possible to have too much moonlight. The light is meant to mimic the light of the moon so imagine how weak that light is for us typically and then add water as a buffer. Your reef tank shouldn’t be glowing with the light generated from the moonlight machine. Instead, it should be slightly better than dark. You can make out some fish, but you can’t read the user manual that your moonlight came with. That might sound like a downer, but the aquarium will still look great even with the minimal light intensity.

How long can a reef tank go without light?

A tank can go a while without light; it’s the specific livestock in the tank that you need to consider. Some people will do “blackouts” where they attempt to remove the algae from their systems by cutting off the light from entering the tank. I personally wouldn’t recommend this practice since there are safer ways of dealing with algae, but a person, who might have a power outage or whose reef lighting recently broke, can get away with no more than 3 days of darkness. Even that is pushing it for your coral and plants’ health.

However, the point of highlighting this practice is that you have time to adjust the lighting in saltwater aquariums. You shouldn’t feel like you are moments from disaster if your lighting isn’t perfect from the start. Take some deep breaths and focus on the behavior of your tank. It will tell you all there is to know about its needs.

What are the dangers of having too much aquarium light?

As we have discussed, saltwater aquarium lighting is really important to facilitate plant and coral growth in your tank. It also helps to set a routine for your fish community. However, light stimulates more than just the growth of plants and coral; light can also make algae bloom in your tank. it can do this without even being an intense light. The algae is also a useful way of determining if you have too much light in your tank, though you will want to make sure that your algae are not caused by another factor like water quality first. The last thing you’d want is to address something that isn’t an issue for your tank, which would only cause a second issue on top of the original one.

It only requires enough time, so the best thing that you can make it a practice is to try and reduce the running time of your lights. Try to keep to a day/night cycle. Not only will this help to set establish that routine for your fish, but it will help to make the algae growth in your tank much more manageable for your cleaning crew.

Lighting requirements for saltwater aquariums with only fish and live rock

Not everyone in the aquarium hobby is interested in keeping corals in their tanks. That is completely reasonable and should allow for a little more freedom in setting your saltwater aquarium lighting. In general, as long as you are providing light, you probably will be alright but let’s talk specifics. An aquarium lighting system that uses only 1-2 watts will be satisfactory enough for the needs of your fish.

You might also want to take a general room temperature measurement to see how bright and long you want to leave your lights running. Remember that lights can affect the overall temperature of the saltwater aquarium, so having intense lights in an already warm room could prove hazardous.

Final thoughts

By following this saltwater aquarium lighting guide, you should now be better prepared to investigate your own lighting solution for your aquarium. There are a lot of choices available to you, but you also have time to adjust as you learn. Your corals aren’t going to die the second they are placed in lighting conditions that aren’t ideal, and your fish aren’t going to go blind. However, always monitor the behavior of your tank’s inhabitants so you can accurately and quickly remedy any issues that might present themselves.

Reef tanks have specific needs when it comes to their lights; whether you choose LEDs or fluorescent lights, the choice is ultimately yours and your wallets. Part of the decision is just what kind of lights do YOU want to work with? What system seems like something you can find yourself tweaking and adjusting to fit what you desire in your tank. Whatever you decide, you’ll find the system that works best for you.

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