Ever since the news dropped way back in February of 2020 that Neptune Systems was working on an aquarium light, hobbyists have been clamoring over the Neptune Systems SKY LED and the innovation it might bring ...or lack thereof. 
In terms of LED lighting, Neptune is late to the party with hundreds of successful LED lights already on the market, what could they possibly do better or different that would make their SKY light stand out?

Let's find out in this BRStv Investigates as our hosts, Ryan and Randy, break down the PAR, spectrum and spread data to find out exactly how the light measures up to its competition.  

What Is The Neptune Systems SKY LED Good For?

  • T5 like shadow performance, ideal for SPS corals
  • Eliminating both the disco effect as well as overwhelming shimmer
  • A modular design that doesn’t have 10 different cords
  • A lower price per par than half of the other lights we tested
  • Can be used over a larger than 24” square area
  • Apex ready

What Are Some Challenges With The Neptune SKY LED?

  • Very good light for soft corals and LPS, but certainly not the most affordable.
  • The spectrum is not as wide as half of its competitors
  • It has a larger form factor that some reefers just won’t need

Par: Bang For The Buck

PAR supports life in our aquariums and provides nearly all of the energy a coral needs for metabolic function. By evaluating the cost per PAR we can capture data that allows us to gauge cost-effectiveness across and compare against competing lights. 

To calculate using a PAR meter, we measure 36 unique points over a 24" x 24" area with the fixture mounted 9” above the water level. We then take the total retail cost of the fixture and divide it by the average PAR from those 36 points.  Of course, the fixture output settings make a big difference so we make two evaluations.

Cost Per PAR

With all output channels at 100%, the average PAR was 390 which gives us a cost per PAR of $2.23. Compared to the historical data, the average of all the lights we have ever measured was $2.10 meaning the Neptune Systems SKY is right in line with competing LED fixtures.

"Usable" Cost Per PAR

Most reefers will not use this light at 100% intensity on all channels so we also measure using a BRS Custom output setting which is designed to be more realistic in terms of the settings a hobbyist would actually use over their tank. We reduced the amber and green color channels by only 25% which resulted in an average PAR of 380. This brought our "Usable" cost per par to $2.29 which was significantly less expensive than the last light we tested. 

What Kind Of Corals Can It Support?

To perform this test we take a 24-inch cube aquarium and measure the par at 6, 12, and 18 inches deep. We take 36 points to provide a map of the par readings to see how certain types of coral would fare throughout the tank.


  • We found that running the BRS customized settings at 70 percent will allow for a great environment to keep SPS corals
  • To keep these SPS corals, we were looking for a par window between 200 and 350 with as many points in the top, middle, and bottom of the tank within that range
  • 76 out of 108 or 70% of the points taken were in the SPS zone of 200-350 par
  • There is no question that the Neptune SKY LED is capable of producing the type of energy SPS corals require in a 2’ x 2’ x 2’ area and it can go even bigger


  • Through running the BRS custom settings at just 25 percent we were able to create an ideal environment for LPS corals.
  • 80 of the 108 points or 74% of the area was in the ideal par range of 75-150 for keeping LPS.
  • This is not the most cost-effective light for keeping LPS corals, but if you are looking for an alternative to T5 this is a great option.


Neptune Systems has rated this light for a maximum spread of 30” x 36” x 30”. Through our testing, we have found that the ideal mounting height to maximize both par and spread is 9” above the waterline.

  • To get the mounting height of 9” we raised it until 15% of the par spilled out of the tank and into the room.
  • The Neptune SKY LED does not use additional lenses.
  • We measured a 47% drop in light from the dead center to the outside edges of the tank at 6” below the surface. This ranks amongst the middle of the pack when it comes to its competitors with the lowest being 20% and the highest at 80%.


High Contrast & Hard Shadows

Shadowing is an important consideration when selecting the proper light fixture for your reef aquarium. On one hand, having high contrast and hard shadows can cause many parts of your corals to not receive the light they need to thrive. This would mean that most of the light the coral is receiving will only be coming from one specific angle.

Low Contrast & Minimal Shadows

Having low contrast and minimal shadows is what you are looking for out of your light fixture. This would mean that your corals are receiving light from all possible angles and there are very few shaded spots that could cause harm to a coral. This is really only possible when the light fixture is larger than the item you are trying to illuminate. This is why T5 fixtures remain a popular option for reefing hobbyists.

How The SKY LED Performed

The SKY LED performs similarly to a T5 fixture when it comes to shadowing and contrast. Due to its large form factor and diffusion, it does a very good job of illuminating nearly all parts of the corals within this tank. Other than the slight amount of shimmer from the SKY, most people would not be able to differentiate between it and a four-bulb T5 fixture. With form factor playing an important role when it comes to coverage and shadowing, it seems that we will start to see more of a transition from small compact fixtures to larger fixtures. Simply put, larger form factor fixtures provide more thorough coverage with light coming from every angle. Small form factor lights work well for corals that encrust or grow low to the surface like Zoanthids and mushrooms. That being said, these same compact fixtures will not be great for corals that branch because as they grow they will shade each other out.


ATI Blue Plus Vs. SKY Custom Spectrum

The ATI Blue Plus spectrum is considered to be the holy grail of spectrums when it comes to coral growth. In comparison, the spectrum of the SKY LED is narrower. It is important to consider that the readings on the spectrum graph are in a ratio and just because the Blue Plus looks wider, it does not mean that the SKY isn’t capable of those measurements, it simply means that they are in a different ratio.

Adjusted SKY Spectrum

To make the spectrums more comparable, we again made some slight adjustments to the SKY settings by turning the blue channel down to around 50% and kept everything else the same. This may appear now like the spectrums are significantly more similar but in actuality, all we did was shift the spectrum ratios.

SKY Vs. Other Similar Light Fixtures

All of the spectrums on these fixtures are unique but none of them perfectly fill the ATI Blue Plus. You could say that the SKY LED falls right in the middle of the pack when it comes to creating a spectrum optimized for coral growth

How Are Corals Collecting This Energy

Corals use the following three elements to collect energy for their overall health and growth. With that in mind, this is where the SKY can set itself apart from its competitors.

  • Chlorophyll- A: Has an initial peak at around 430 nanometers which is right in range with the SKY LED.
  • Chlorophyll- C2: With a peak nanometer reading of right around 450, this allows the coral to absorb nearly 50 percent more energy than if it peaked at 460 nanometers.
  • Carotenoid: The peak absorption rate is once again around 450 nanometers 

Spectrum Blending

This is a grid of LEDs that can be difficult to mix without a disco effect. Both the diffuser as well as the acrylic plate beneath the diffuser helps to blend the light before being released into your tank. To measure how well it blends the light, we put the spectrometer underneath the tank and have the water flow going so it starts to refract the light. Then, we take 10 shots to see how well the spectrum is blended. The Neptune SKY Performed as well as you could ask as the spectrum looked nearly identical in every shot that was taken. The only light that beat this was the T5 itself which doesn’t even shift color.

Spectrum: Ease Of Getting It Right

The smartphone application makes it very simple to program and schedule the light to run on your system. Reefers can also run the setup task on their phone or computer. There is a Neptune recommended setup and you can also replicate the BRS settings that we used for our testing. You can mess around with the settings to find something that you like and if you don’t save it, it will revert to its saved program after a few minutes. Additionally, running the task will group all of the SKY fixtures you have and program them collectively. There aren’t that many sliders that make programming these lights complex and confusing. The light was built to have a visually appealing and coral growth-oriented spectrum when all of the sliders are at 100%. If you don’t know where to start, just max out all of the sliders and adjust the overall intensity to suit your needs.

Visual Appeal, Does It Make Corals Look Awesome?


  • Neptune SKY Diffused Shimz: If you don’t want any shimmer coming from your Neptune SKY LED these Shimz inserts will plug directly into the holes on the diffuser. They will ensure that none of the shimmer makes it into your system.
  • Ecotech Mounting Options: The Neptune SKY LED has been made compatible with all of Ecotech’s mounting solutions for their Radion XR30 G5 light fixtures. The RMS Arms and Track will allow you to perfectly position your SKY fixture.

Your Questions

Are we only talking about this light because Neptune Systems is now our sister company?

No, we have done the BRSTV Investigates on numerous light fixtures and we will continue to cover more of them to help hobbyists make the right choice for their reef tanks. This series exists to present the data we have uncovered by testing these lights. How you interpret the data is completely up to you.

Why aren’t your Par goals for SPS systems much higher?

The 200-350 par values we shoot for when it comes to SPS is based on what World Wide Corals aims for in their systems. These values are also based on what we have found to be successful in our tanks here at BRS. Ryan has found that a lot of the time, the high par measurements were taken at the top of an aquascape which is not representative of the average values within the entirety of the tank.

What would you guys change about this LED fixture?

Some people may prefer that Neptune add more pop-outs to create more shimmer for visual appeal. We feel that making the spectrum a little bit wider would be beneficial, but it is already hitting the right peak. Besides a bit more shimmer and a slightly wider spectrum, there isn’t anything else we could point to for needed improvements at the moment.