You might be asking “how many watts of LED lighting do I need for a reef tank?”. Well, this might seem to be a fair question to ask, but unfortunately asking this question this way is a category mistake and thus a wrong question. It is because LED lighting differs from the fluorescent or metal halide lighting and the parameter of judging the output is also different.

So, if you ask how many watts of LEDs you need for your per gallon of water or surface area in the reef tank, you are not asking the right question at all.

LED fixtures simply do not follow the watts per gallon approach. When it comes to LEDs, the experts consider PAR (photosynthetically active radiation) going into the tank instead of watts per gallon approach as the standard to judge the need for LEDs in your reef tank.

In this article, I am going to talk about the PAR approach in detail including how much PAR you need for your reef tanks. You will also know why we use lights in the aquarium in the first place. The mystery of LEDs’ popularity for reef tanks will also be demystified.

I will also discuss the features you have to look for while buying LEDs for your tank along with other related topics. Just keep reading.

how much LED light for reef tank

Is Visual Brightness a Logical Parameter to Guess the PAR Amount?

The answer to this question is a big ‘no’. When it comes to the light spectrum, the viewpoint of humans and corals is different. What we as humans see as brightest is limited to 560 nanometers. On the other hand, corals in the reef tank that depends on photosynthesis experience blue and UV range lights that we are unable to see with naked eyes.

That’s why it is a blunder to guess the amount of light just by depending on the visual brightness that we humans experience.

And it will be a mistake to apply our definition and parameters of light while we are arranging lights for the sea corals and plants. If you use too much light in the tank, you are likely going to bleach the corals. Using a PAR meter is the only solution to find out the amount of PAR going into the tank from a certain distance.

How Can You Evaluate LED Lighting Performance?

Well, first of all, we urge you to forget about LED watts per gallon or watts per gallon LED approach if you intend to use the LEDs for your aquarium.

It is not electricity that is required to grow corals, rather it is light that is important. If you use electrical metrics for judging the LED fixtures, you are not doing the right thing. This kind of evaluation system is not going to give you any accurate information about how much or less light (PAR) your reef tank is receiving.

One of the reasons for this is that PAR (PAR/watts) efficiency varies in the offered LED fixtures of different manufacturers.

So, if you evaluate the input in terms of the watt, it is likely that you are going to supply either 2x or 0.5x of the desired PAR.  So, it all depends on the efficiency of the PAR rather than anything else.

If you want to compare the fixtures, you can use a PAR map. A PAR map can help you determine the amount of PAR your tank is receiving at various locations and depths.

How Much LED Lighting Do You Need for a Reef Tank?

The type of corals and depth of water determine how much LED lighting do you need for your reef tank. These parameters will help you to determine the PAR and spectrum you need to supply into the tank. However, for your benefit, here I have come with a list on the minimum range of PAR you will need to ensure in your reef tank for the healthy growth of corals:

  • Tanks dominated by soft corals: 50 to 100 PAR of LED lighting
  • Tanks dominated by LPS corals: 50 to 150 PAR of LED lighting
  • Tanks dominated by SPS corals: 250 to 350 PAR of LED lighting
  • Tanks dominated by mixed corals: 75 to 350 PAR of LED lighting

When it comes to the recommended time of LED lighting, I would recommend you to ensure a full photoperiod lasting for 9 hours. In this 9 hours, 7 hours should be of core spectrum period, 1 hour of the ramp-up period, and the remaining 1 hour of the ramp-down period.

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How to Measure PAR in Your Aquarium?

There are PAR meters available in the market that can help you measure PAR in the aquarium. To get an accurate result you have to make sure that your PAR meter is of high quality and capable enough to output exact PAR value. Understanding the PAR map is the most essential thing that can help you place the corals in your reef tank at the right place.

If you own a PAR meter you can easily determine at what height the corals should be placed so that they remain within the range of the recommended PAR value (for example, 250 to 360 for SPS corals).

However, do you know where to get the PAR meter? First of all, see if any of your local community owns one and can lend you to use for your reef tank. There are many reef communities that offer its members the required tools including the PAR meters for their members.

However, if you cannot use the first method, you can buy or rent it from any recognized suppliers or manufacturers. Beef Reef Supply, for example, sells and also lets the tank owners use PAR meters in exchange for rent. They charge about $70 as rent and take a deposit of $450 as the security money. To get the full security money back, you are supposed to give the PAR meter back within the 7 days of renting.

You can also buy combined reef monitors such as the Seneye Reef Monitor. Apart from finding the PAR value, combined reef monitors can monitor free ammonia, pH level, temperature, etc.

Use of Lights for Reef Tank Aquariums

Lights in the reef tank aquarium may serve either one of the following two purposes:

  • general or aesthetic purpose and
  • functional or specific purpose.

While the general lights merely add beauty in the aquarium, the functional lights work as an important factor in completing the biological process inside the reef tank aquarium.

Aesthetic lights might seem beautiful to the aquarists, but it does not help the tank inhabitants in any way. On the other hand, functional lights are very crucial when it comes to fish and coral growth.

No matter which purpose you want to serve, you need lights. With a particular primary lighting setup, you can either create the natural lighting conditions to preserve a healthy ecosystem in the reef tank aquarium, or you can adorn the tank with creative and dramatic lighting effects.

Let’s now explore the purposes of lighting in a reef tank in a bit detail.

Aesthetic Use

Aquarium lights, when used for aesthetic purposes bring out the amazing and vibrant color of the fishes and corals. Color Rendering Index or CRI indicates the visual quality of a certain kind of light. The scale of CRI ranges from 0 to 100. While 0 signifies the least natural daylight condition, 100 signifies the highest presence of it.

If you want to get the visual effects close to the natural sunlight, you have to buy full-spectrum bulbs or bulbs that are capable of emitting all the wavelengths of the visible lights. The more the effects and proximity to the daylight you get from a bulb, the higher will be the CRI range or value.

But, you should know that a high CRI value does not indicate that a bulb will output the best color. Many color-enhancing bulbs use the warmer color spectrum (ranging from red to yellow) to give you the best augmented and enriched color experience.

That’s why it is a good idea to combine the power of both full-spectrum lights and color-enhancing lights to get the best color without sacrificing the natural appearance and health of the tank inhabitants.

When it comes to visual quality, the color temperature of the bulb is another important aspect to consider. Color temperature is generally signified by K-rating and measured by degrees. Lights that have lower K-rating produce warmer color spectrum such as orange, yellow, and red. On the other hand, lights with higher K-rating produce cool colors.

Functional Use

Like freshwater aquariums, lighting is essential for photosynthesis in reef tanks. The plants and corals in the reef tanks are photosynthetic organisms that need light to manage their foods.

When we are talking about sustaining lives in the tanks, the intensity of the bulb is a crucial factor to consider. Many aspects affect the intensity of the light. When you select any light fixtures, the total wattage plays an important role. The higher wattage translates into greater light intensity.

Simply put, the higher wattage a bulb will feature, the greater will be its lighting effect. So, if you have got a reef tank aquarium that requires a high intensity of lighting, you should go for light fixtures that can serve you with higher wattage output.

Usually, you will need 2 to 5 watts of lighting (not LEDs) per gallon for freshwater aquariums. However, if you have got a fish-only aquarium, just 1 to 2 watts (not LEDs) of lighting per gallon will do. But, when it comes to reef tank aquariums, and you are going to use LED fixtures, things are going to be different.

If you have SPS dominated reef tanks, you will need to use higher PAR that might go up to 350. On the other hand, Soft coral dominated tanks might need to receive 100 PAR and LPS dominated tanks might need to receive up to 150 PAR. However, the amount of necessary PAR varies from reef to reef for a variety of reasons.

But, how do you calculate the watts a gallon receives from the light fixtures? It is not very difficult to find out. Just divide the supplied wattage with the number of gallons you have set in the aquarium. And that result you will see is the answer. For example, if you have got a 29-gallon aquarium where you have set 65-watts lights, it means that the aquarium inhabitants receive about 2.24 watts of light per gallon.

Though this amount of light can be adequate for any freshwater aquarium, it is too high for fish-only aquariums and too low for reef tanks or saltwater aquariums. However, as we mentioned earlier, this is an old method applicable to old metal halide lights and does not work well with LED fixtures. We should use the PAR standard from now on to ensure the perfect light in the reef tanks with LEDs.

Lighting requirements may vary for a lot of other reasons such as differences in fish species, types of corals, tank depth, and many more. So, make sure that you study the lighting requirements for different species and then supply the wattage accordingly.

Why Should You Use LEDs in Your Reef Tank?

LEDs are popular in the modern world due to the benefits they offer. Let’s see some of the advantages of using LEDs in the reef tank.

Freedom of Choice: You are at liberty to buy LEDs that differ in price ranges, types, styles, brands, and models. You can choose to use DIY LEDs or commercially available LEDs ranging from cheap to expensive.

No matter what your budget, choice, or requirements are, you are likely to get LEDs that are suitable to meet your needs. You can choose them either for aesthetic use in tanks or to meet functional purposes such as keeping the corals healthy.

Low Energy Consumption: One great advantage of LEDs is that they are energy-saving. You do not need to carry high electricity bills at the end of the month. So, though they might seem costly to buy at the beginning, they give you the cashback when you use them for the long-term.

Less Heat: Another advantage of LEDs is that they do not emit as much heat as fluorescent and incandescent lights. The light-emitting diodes rather than the use of bulbs help LEDs stand apart from the crowd. The low temperature will keep the fish and corals in good health. Because excess light or heat can create stress in them and create an imbalance in the aquarium ecosystem.

Durability: To talk about durability, can you compare anything that can defeat LEDs? They can last even up to 30,000 hours if you buy the light fixtures from a good brand.

Flexibility and Compactness: Flexibility in the layout has also contributed to making LEDs popular. It is unlikely to get such flexibility in other types of lights. You can place them anywhere in the tank. Be it spotlighting certain areas of your aquarium or covering the entire tank, you will find LEDs to serve your purpose flawlessly.

On top of that most of the LEDs are compact and easy to carry anywhere you want. You can also make adjustments as required.

One good news is that waterproof LEDs are also in the market now. You will be able to mount them underwater and clean your tank whenever you want.

Safe to Use: When it comes to safety, LEDs are way safer than T5 or T8 fluorescents and old metal halide lights. No noxious gasses or metal filaments are used in LEDs that make it very safe to use.

Essential Features to Look For While Buying LEDs for Your Reef Tanks

Installation Process

All the reef tank owners are not engineers! It is not an easy thing for many to understand the technical description of the LED manufacturers and follow the instructions accordingly.

If you find technical stuff hard to deal with, you should look for buying LEDs from a manufacturer who supplies LED lighting with most of the parts assembled. That will save you time and brain.

Lighting Capabilities

The type of light you get on different channels is important. To experience the best lighting facilities, some lighting systems let you add lights of different colors. It is certainly helpful for the growth of marine life along with creating a better mood.


Is there anyone who does not want their LEDs to last longer? The answer to this question is ‘no’. You can see the durability of the LEDs in the product label. Product durability depends on model, price, quality, and brand as well.

You will find many LEDs that have a lifetime of 30,000 hours. Will you buy LEDs that come with 10,000 hours even if you are offered the half price of the previous one? Of course not.

Product material is one of the important aspects to look at when you are looking for durability as it is one of the key factors that determine durability. You should always purchase LEDs that last longer and do not require frequent replacement.

Ease of Use

If you do not want to engage yourself too much in technical aspects, it is better to choose LEDs that are designed to be simple and easy to operate.

Though some lights might have great functionality if those lack in ease of use, very few people would choose them.

So, choose lights that are not a nightmare for you. Lights that have a variety of controls might be tough to handle.

Power Consumption

LEDs indeed consume comparatively less power than other sorts of lights. However, it is still better if you can find the lights that come with power-saving technologies.

One of the main purposes of buying LEDs is to save energy and energy cost. That’s why you need to use a system that fulfills your expectations with the least cost and energy.


Products from good brands are generally packed with high quality. Though products from established brands might seem costly to buy, they are worth the money you pay.

It is always better to take suggestions from other reef tank owners near you to find the best value LEDs. Our suggestion is not to compromise with the quality even if that might seem costly at the beginning.

The after-sales service you will get from the good brands will never match with low-quality brands.

How to Use LEDs at Day and Night in the Aquarium?

Though the fishes keep their eyes open, it does not mean that they hate beauty sleep. If you can mimic the natural environment of the seawater in your reef tank, that’s the best for your fishes. Try to bring an atmosphere where they feel comfort, ease, and at home. It is best to maintain the light as they get in the seawater.

When you are choosing LEDs, make sure that you are buying two types of lights. The bright and white LEDs should be chosen for the daytime. On the contrary, you should choose soft and blue lights for the night. It will provide them a sleeping environment and you can still enjoy their beauty at night. Make sure that your lighting schedule corresponds to their sleeping schedule.

When you will purchase LED fixtures, make sure that they contain both white and blue lights. However, if you buy a package with a mixed type of lights, you are supposed to get fewer blue lights than the white ones.

For example, if you buy a package of 21 LEDs, you might receive 18 white lights to illuminate the aquarium at daytime and 3 soft, blue lights to illuminate the aquarium at night.

In case you have a good budget for lighting, you can go for buying the LED fixtures that come with auto-timer settings. If you do so, white lights will automatically go off when the day starts to fall. Firstly, this will save your time, and secondly, you do not need to remember switching off the white lights at the end of the day.

How To Get The Best Of LED Lighting To Maximize The Growth And Coloration Of Corals?

Now that you know almost everything about lighting and LED lighting for your reef tank. Here’s how to use LEDs so that you can maximize the coral growth by getting the best possible output of your LEDs:

Let the corals feel at home: One rule of thumb is to choose an amount of light that makes fishes and corals at home and not in stress. Adding too much or too few lights in a tank will interfere with their eating habits and sleeping cycles. While choosing the amount of light, you should think about the depth of the tank.

Keep your focus on three key aspects: While you are using LEDs for your reef tank, you have to keep 3 things in focus: light distribution, power intensity, and the PAR spectrum.

Firstly, by light distribution, we mean that the light should cover the entire tank. To ensure this, you might require more than one LED fixture.

Secondly, light intensity should be in a way so that it makes sure that the LED can supply the required amount of PAR.

And finally, the spectrum has a direct influence on coral growth. SPS, LPS, and soft corals do not respond similarly in a certain color spectrum. Make sure that you have set the right color spectrum for day and night so that your corals can have proper metabolic functions and thrive.

Excess PAR does no good: Keep it in mind that more PAR than required is not healthy for the corals. It can rather bleach and kill them. Many LEDs can supply 2 to 3 times more PAR than your corals required. You have to be careful not to use LEDs without determining the PAR by a high-quality PAR meter.

Start with lower intensity: When you start using LEDs, begin with a lower intensity setting. You can increase the intensity gradually and reach higher recommended levels.

Make adjustments monthly, not daily: You are not supposed to change your lighting or spectrum status every day. Frequent swings in the intensity or spectrum of lights can just destroy your corals. If you need to bring any change, adjust them after about 1 month. Make your adjustments slowly to let the corals get accustomed to the change.

Use an LED controller: To adjust the light intensity, you should consider adding a controller in your LED fixture. Many manufacturers have come with controllers with a variety of features for easy control of the LEDs. Choose one that offers high-quality and easy settings.

Final Thoughts

Have you understood now that asking “how many watts of led lighting do I need for a reef tank?” is this question wrong in the first place? We hope that you have understood the PAR approach which is the right parameter for LED lighting usage.

Buy or rent a PAR meter, calculate the PAR and use the PAR into your tank as per the coral types. The required amount of PAR will be different for LPS, soft, mixed, and SPS corals in the reef tank.

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