Neptune Systems

PMK PAR Monitoring Kit

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$339.99 $339.99

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Features and Benefits

  • Performs continuous light-level monitoring for your aquarium
  • Measures actual PAR – the light corals and plants use
  • Prevents burning out corals
  • Includes ASM – the new Advanced Sensors Module
  • PAR sensor hides nicely in aquarium inside Real Reef Rock
  • Fine tune your lighting to the needs of your aquarium


Continuous light-level monitoring for your aquarium

With the PAR Monitoring kit, you can monitor and log your aquarium’s light levels 24 hours a day! The perfect tool to fine-tune your lighting on your tank. Now you now can adjust your lights with the confidence of knowing you will not be giving too much or too little light to your corals and plants.

Prevent Burning Out Corals!

At certain parts of the spectrum, the human eye cannot perceive light intensity changes once the light level exceeds a certain point. Too often this causes people to adjust their LED lights far past the ideal PAR level for their corals or plants. This usually results in burning, bleaching and/or death. With the PMK you can adjust your lights while monitoring exactly what light is affecting your corals and plants throughout the day. Also, not all corals are alike. Each type of coral has its own range of light intensity that makes it happy or not. 

Rugged Sensor Hides Inside Real Reef Rock

Sensors and probes are great in our aquariums, we just don’t want to see them! That’s why we usually put them down below in the sump. Not possible here. Knowing this we had the guys at Real Reef Rock design a custom piece of rock to hide the sensor in your aquarium. Now you can monitor light 24/7 and never see the sensor!

Measures Actual PAR – The Light Corals and Plants Use

The Apex with the PMK measures actual PAR. PAR stands for Photosynthetically Active Radiation. This is the light from 400 to 700 nanometers that organisms are able to use for photosynthesis – this includes the zooxanthellae algae that lives inside your corals. Other measurements like LUX are not useful at all as they measure just the light visible to the human eye.

24/7 Light Monitoring!

Track your light levels over time. With the PMK you track and log PAR 24/7. Now you easily go back and look at how you had your lights running last week. Even better you can compare your light output across the day with others who use the PMK and then compare light schedules and LED settings.

No more guesswork!

If you control your lighting with the Apex, you are in for an added bonus. The lighting wizard in Apex Fusion shows you your previous days light level across the day superimposed with the light wizard graph. Up until now, you had to pretty much wing it when it came to making adjustments. Now you can easily make lighting changes and see the effects of those changes in one simple interface!  If you don’t have it already, this is one major reason to start controlling your lighting with the Apex. There are many Apex Ready light choices available. Some of the wireless lights like those from AquaIlluminations and EcoTech Marine even have their own Apex control modules (AWM and WXM).


Includes the newly released Advanced Sensors (ASM) Module!

More information will be released on this module in the future but in short, this new module allows for hundreds of different types of future Neptune Systems and current 3rd-party sensors to be connected to your Apex and have their data logged.


Kit Includes:

ASM – Advanced Sensors Module

NPS – Neptune PAR Sensor

Real Reef Rock

6′ AquaBus Cable


pdfNeptune PMK Instructions

More Information
UPC 748252989307
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Product Questions

Does this work with the Apex classic ?
Question by: Aaron Brewster on Nov 3, 2022, 9:32 PM
The Neptune Systems PMK will work with an Apex Classic.
Answer by: Scott F. (BRS Staff) on Nov 9, 2022, 12:20 PM
Can I order a replacement ASM module for this from you guys? I don't see it anywhere.
Question by: Perry D Jenkins on Mar 25, 2022, 3:34 PM
Hey there,
Thank you for reaching out to us. Unfortunately, we do not carry that module as a stand alone item.

Please let me know if you need anything further and take care!
Answer by: Matt Lucero (BRS Staff) on Mar 29, 2022, 10:53 AM
Will this work with the APEX "Classic" or only the new APEX controller that came out recently.
Question by: Edward Bowman on Mar 19, 2018, 12:14 AM
Hi there,
Thank you for reaching out with your question.
The PMK will work with the newest version of Apex as well as the Classic version.
Please let us know if you have any other questions.
Have a great day!
Answer by: William Glenn on Mar 21, 2018, 12:25 PM
I have the 48" ATI dimmable T5 (6 bulb) unit and the newest Apex System (the $799 one). First question is will the Apex be able to adjust the lighting for me so I can bypass the dimmable function on my ATI? Second question is do I still need the ASM with this version of my Apex to get par values? Thanks!
Question by: Vincent on May 9, 2017, 9:07 AM
Hey there,
While the Neptune can control on/off functions for lights, and can connect to many LED fixtures for dimming control, ATI has now integrated the control into their fixures and they don't have a way to connect the 0-10v control to the Apex. If you wish to monitor PAR through the Apex, you will still need the PMK/ASM module setup as this function is not integrated into the base unit.

Happy reefing!
Answer by: Zack on May 14, 2017, 10:49 AM
How long is the cable for the par meter?
Question by: Guillermo Ramos on Dec 10, 2016, 10:37 PM
Great question! That cable is 15' in length. :-)
Answer by: Admin on Dec 21, 2016, 6:52 PM
Do you have to buy one of the Apex systems in order to be able to use this? Or does it work on it's own?
Question by: Jamie Springer on May 26, 2016, 8:32 PM
Hey Jamie!

Great question! You will need an Apex Controller in order to use the PAR Monitoring Kit.

Answer by: Randy on Jun 2, 2016, 11:55 AM
Have you guys used this product in your tanks with LEDs? Does it really work? How does it compare with the expensive PAR meter you guys have?

Question by: Emmanuel Becerra on Mar 23, 2016, 12:55 AM
Great question!
We have used the PAR meter for Neptune systems in our T5 and Metal halide tanks with great success and it works as well as any PAR meter currently available. For LED PAR readings will be slightly off depending on what color LED is turned on and will not give 100% accurate readings for growth. You will want to consider the Seneye as an alternative option which has better reading of LED light. Feel free to let us know if you have any further questions!
Answer by: Connor on Mar 23, 2016, 10:50 AM