LED Aquarium Lighting in a Reef Tank & How to Select the Right One

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There is a lot of confusion when it comes to LED lighting for reef tanks. They look great and provide a lot of benefits to your reef tank, they are pretty technologically advanced. However, a number of reefers have reported mixed results with LEDs and the specs on these fixtures are not exactly universal, unlike traditional T5 lighting. We created this article to assist in the LED selection and buying process. Our goal at the end of the article is you been given the knowledge to select the best LED system for your tank:

Why LED Lighting?

There are a ton of reasons why reefers consider LED lighting. The biggest reason is the fact that you will never need to buy replacement lights ever again because of their long lifespan. This saves a lot of money and cuts down on the most common maintenance issues with traditional T5 and Metal Halide lighting. They are the most energy-efficient lighting setups and will cut down on energy consumption in the home.

LED lighting is also controllable and offers all sorts of customization to suit your individual tank needs. This means that you do not need to find different types of light bulbs to suit your tank as you can just adjust the spectrum either manually on the light fixture itself or through controller software via an app.

The PAR and spectrum output on LED is also very consistent. When you use T5 or Metal Halides, the output of the bulbs will change over time requiring replacement. With T5 the best practice has typically been to replace half your T5s every 9-12 months. This is done in this fashion so that you always have fresh lights running in your tank, but does get pricey.

LED light is also very low profile allowing for very attractive setups. They can be mounted on rails, suspended above the tank, mounted on the aquarium, etc.  They also offer a shimmer effect that compares with a Metal Halide setup.

LED, while expensive upfront, is actually cheaper than traditional T5 and Metal Malide setups over the long run. Along with the cost savings in electricity, there is a significant cost saver over a 5-year period when considering bulb replacement costs.

Cons of These Systems

Looking at the list of the benefits of having a LED setup, it makes it seem like a no-brainer to select an LED setup over anything else. However, we need to discuss the disadvantages of LED systems.

The biggest disadvantage to LEDs compared to T5 and Halides is the fact they are not exactly plug-and-play. This is likely the reason why some hobbyists have experienced mixed results with LEDs.  You have to keep into account intensity, spectrum, and positioning with LEDs to make sure they best fit your tank.

This is where we need to take a step back from the fancy tech of LEDs and really focus on what matters – providing the proper light for our corals so they can thrive. It’s very easy to get caught up in the gadget and tech of LEDs or play with what looks the most visually appealing, but at the end of the day providing the proper light intensity and spectrum is the most important aspect.

This is what can make LEDs complicated. Many reefers will not have knowledge of what proper PAR and spectrum levels are needed for their corals and have not really thought much about other factors like spacing or shadowing effects.  Many of us in the reefing community also do not have access to lighting tools that would tell us what our PAR is to efficiently measure our light intensity…we just use our eyes or our experience.  To help guide you on proper light selection, we need to define a few things for you – namely, what is PAR and what is Spectrum.

So What is PAR and How Does It Relate To A Reef Tank?

PAR, or Photosynthetically Active Radiation in our hobbyist terms is the number of particles of light that fall in a square meter over the course of one second that is in between the wavelengths of ~400nm to 600 nm.  NM stands for nanometer or billionths of a meter. Non-scientifically speaking it is the measurement of the total amount of visible light that shines on a square meter after one second.

PAR is important to reef tanks because it is a measurement of how much usable light energy is available to your corals. It is one of the easiest ways for you to measure and gauge the exact amount of light your reef aquarium is receiving – which is extremely important when it comes to LED lighting.

Why is this so important for LEDs? The main reason why is because LEDs are the most intensive lighting systems you can buy on the market. Several of the higher-end LEDs will outperform metal halides in PAR ratings and will need to turn down to avoid coral deaths. Knowing this, adjustments may be necessary for your light fixture and we have to understand that it is actually better to have too little light than too much light for a coral. Corals can be pretty adaptable and can survive months of too little light, which will give you time to adjust and provide the correct lighting for them.  However, too much light will cause a coral to pass away within days! It’s no wonder knowing this now that reefers can have mixed results with LEDs!

Now that you know what PAR is, we need to explain what are acceptable PAR ranges for your aquarium. Keep in mind these are general recommendations. Particularly with SPS corals, the range can vary widely. Also, keep in mind that PAR ranges are higher at the top of the tank and lower at the bottom of the tank. What this would mean is if you got a LED fixture that produces around 300 PAR at the bottom of a tank, at the top of the tank you would likely be producing over 500 PAR.

SPS – 150~300 PAR
LPS/Softies – 25~100 PAR

What is Spectrum And How Does It Relate To A Reef Tank?

For our discussion about the spectrum, we are going to concentrate on the visible light spectrum. Visible light is a form of electromagnetic radiation and is defined as the wavelengths that are visible to the human eye. The wavelengths are measured in nanometers. These range from 400nm which is ultraviolet to 800nm which goes to infrared.  When it comes to reef tanks, we are concerned with the following colors:

Blue (420-460nm) – Most important
Green – Mostly visual – can increase algae growth
Red – Removed by ocean water in the wild may be more harmful than helpful
Light Spectrum
There are a lot of theories when it comes to correct spectrum – but we lean on the spectrum specs of proven technologies like T-5’s. We will use an ATI bulb as an example as ATI bulbs are a benchmark when it comes to T-5’s. You can see the wavelength range of ATI’s Coral Plus lights below noting the 460 nm peak:
ATI Spectrum Chart

So What Makes a good LED Fixture?

There are 5 things to consider when determining if a LED Fixture is of good quality:

  1. Longevity
  2. Build Quality
  3. PAR Output and Spread
  4. Spectrum
  5. Support and Part Availability

The longevity of your LED Fixture to me is the most important factor in your decision-making. These units are not cheap and should outlast the tank that you are going to mount it on. You can look up reviews on-line and forum comments on the LED brand you are looking up to get the best gauge.

Build Quality is another factor you will want to consider. Ask yourself questions like is the fixture built by a US based company and have they been around in the industry for years? The last thing you want is for a part to break and you have no support because the company is no longer around or their support is from another country like China and they won’t respond to your e-mails.

PAR is the next consideration. Given the LED fixtures that we sell in our store, you will have no issue answering that question – what you likely will need to deal with is too much intensity on the highest-end models that we sell. The PAR spread is also another factor to keep in mind. Some of the models can have very intense lighting in the middle and the spread is less on the outside.  Other models have a fair even spread. In both cases, you will need to factor in spacing to solve get the proper PAR or adjust your intensity on the fixtures.

Spectrum is important if your fixture is not adjustable. This is a critical question to answer if you purchase an LED fixture that does not publish its a spectrum or give you the option of adjusting the spectrum. Other higher-end models allow you to adjust the spectrum yourself to suit your needs, which may require you to adjust it. This can be a pro or even a con as adjustments can get complicated. You will want to look for a light fixture that peaks around the 460nm range, which has been the standard for top T5 lighting manufacturers for many years.

This is where a manufacturer like a Kessil comes in with their simple adjustable features that ensure you always have the correct spectrum for your controls (Called the Kessil Logic), but allows you to remove harmful colors or reduce intensity. They also focused on more even spread than intensity which makes them more suitable for beginner and intermediate hobbyists..

To help simplify the selection process for you, we provided the PAR & Stock Spectrum readings from our most popular LED lighting and our recommendations below.  All readings are at 100% intensity:

MaxSpec Razor
@ 6″: 220-193 PAR at top, 67 PAR at 24″ deep
@ 12″: 128-116 PAR at top, 67 PAT at 24″ deep
Peak Spectrum – 450nm
Best for Mixed Reefs

Kessil 360WE
@ 6″: 189-181 PAR at top, 95 PAR at 24″ deep
@ 12″: 104 PAR at top, 79 PAR at 24″ deep
Peak Spectrum – 460nm
Best for Mixed Reefs

Kessil AP700
@ 6″: 420-380 PAR at top, 176 PAR at 24″ deep
@ 12″: 275 PAR at top, 188 PAR at 24″ deep
Peak Spectrum – 460nm
Best for Heavy SPS
Works for Mixed Reefs if raised higher – Can light a 4′ mixed reef tank

Our last factor is support and part availability.  If your fixture comes with moving parts like a fan, you may need to replace the part in the future. Ask yourself the following questions:

  • Does the manufacturer have quality support?
  • Is customer service US based and easily accessible?
  • Do they carry parts for earlier models?
  • How quickly can they supply parts to you?

These are all factors you need to consider when purchasing an LED fixture. We have a post discussing the Best Reef LED systems on the market that goes in more detail about the best-LED lights available in the hobby today.

Do I need a PAR Meter?

The main issue with PAR Meters is that they are expensive.  If you are going for a heavy SPS tank or large mixed reef setup, it might be worthwhile to purchase one given a $200 investment could save you thousands of dollars in lost corals. We would recommend an Apogee PAR meter (Quick NoteThis post includes affiliate links for which I may make a small commission at no extra cost to you should you make a purchase) if you are looking for one.

If you cannot afford one, it may be possible to get one from a hobbyist club or a fellow reefer. The best bet, however, is to just avoid the very high end of the LED market as they typically are too intense for most reefers’ needs and will likely need to be dialed back to work on your tank. Kessil with its simple-to-use adjustments even spread, and less intensity is best suited for those who want as plug-and-play LED fixtures as possible.  Even the AP700 is a strong consideration for SPS heavy tanks and its PAR testings have shown a very even distribution of PAR.  At the end of the day, we have to keep in mind that too much light will kill your corals much faster than too little light.

We hope this will help you in your decision on selecting a fixture.  If you have any questions about your potential purchase, leave us a comment below.  If you already have an LED fixture, please leave us a comment and explain why you came to the decision of purchasing your fixture.


  1. Thank you for an informative article above. I have a 650L LPS reef tank, 28″ deep, clear water, under 5 Hydra 26 hd led’s. Because I have a deep tank, by today’s standards, would a good light setting be at 14K at a light intensity of 65%. My lights allow me to toggle into K settings from 6K-20K.
    I have been struggling to find a light setting, even that of the hyper driven recommendations of Red Sea, with no green and red led’s on, that seem to satisfy all of my corals. I have always felt that at 14K this was a good middle of the road light for colour and growth.
    Using a Seneye light meter, my readings at the above K and intensity, are around 110-140par at the bottom and 150-200par in the middle of the tank.
    Look forward to receiving your opinion on this matter.

    Thanks Julian Moore U.K


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