When lighting a reef aquarium, it is important to supply the right amount of light for your corals so you can be certain you're meeting their photosynthetic needs.  The only sure-fire way to know you're lighting the tank correctly is to use a PAR meter to measure the amount of Photosynthetically Active Radiation (PAR) in your tank.  PAR is what we use to gauge the amount of light going into our tanks that is actually usable by our corals.

Knowing how much PAR your corals require makes things easy.  If you keep a mixed reef aquarium with different types of corals, the goal is to create zones of PAR where you're hitting the higher PAR numbers at the top of the tank and the mid-lower PAR range toward the bottom.  Then, of course, place your corals accordingly.  

Top down view of corals

Hop much PAR do corals need? 

  • Soft Corals and LPS: 75 - 150 PAR
  • SPS corals 200 - 350 PAR

With adjustable LED lights measuring PAR is especially important because of the available control. One wrong setting with the LEDs and you can not only wind up with an insufficient spectrum but also end up with too much or too little PAR. Needless to say, this is a pretty critical step in the process of building your reef tank, and investing in a PAR meter isn't always high on your list of things to buy. Some local Reef Clubs and Fish Stores have rental programs or you might get lucky and have a friend who will let you borrow one.

BRS also offers a special 60-day return policy for select PAR meters that essentially allows you to return a used PAR meter for a refund less a $100 mandatory restocking fee. While it's not exactly a rental program, this unique return policy gives you an opportunity to use a high-quality PAR meter to set up your lights and then decide whether or not you want to keep it. Should you decide to invest in a PAR meter for yourself, here is what you need to know.

Apogee PAR Sensors

What's The Difference?

We carry a few different options from Apogee plus the Neptune System PAR meter and Seneye Reef Monitor. There are some pretty significant differences between the various PAR meters, all of which are reflected in the cost. 


Apogee is our go-to brand for PAR meters and among the various options, you're going to notice a black sensor and a blue sensor.  The black sensor (MQ-210X and SQ-420) is the original sensor that is best used for metal halide and T5 Fluorescent lights in terms of accuracy. It will work with LEDs, but won't provide as accurate of measurement when compared to the blue, full-spectrum sensor.  The Apogee MQ-510, PQ-510, and SQ-520 are the best choices for measuring LED lighting and utilize the blue, full-spectrum sensor.  

In either case, the sensors can accurately measure PAR underwater and have settings to automatically compensate for light refraction.  Be sure that you follow the instructions and are using the PAR meters with the correct settings for underwater measurement.  

ITC Reefculture PARwise

This PARwise USB Light Meter is a great value because not only does this device measure PAR, but you can also examine your spectrum along with a variety of additional lighting metrics using the single wired sensor.  The small sensor can be used wet or dry and connects via USB or USB-C to your Windows-based PC, macOS, or Android device with Chrome Web Browser. It is capable of measuring fluorescent, LED, metal halide, and even natural sunlight making it one of the most versatile and comprehensive hobby-grade light meters available. 

Neptune Systems PAR Meter

Neptune's PAR sensor is made by Apogee so your get a reliable measurement but it does require a Neptune Systems Apex aquarium controller to operate.  This is great for those of you who already have an Apex and it allows you to record and log the PAR data using APEX Fusion.  The sensor is also discreetly hidden inside an artificial rock so it will blend into your aquascape should you decide to keep the sensor inside your display for extended periods of time. This works great for not only setting up your LEDs but also tracking performance over time and comparing that performance with other reef tank owners! 

Choosing the Right PAR Meter

Of course, the investment cost is always something to consider when purchasing a new piece of gear for your tank. Consider whether or not you want to own your own meter or if you're just looking to use it once while setting up your lights. Owning your own PAR meter does have some benefits including the ability to make confident adjustments to your lighting and monitor performance over time, let alone for use on multiple aquariums. 

The type of connection is also important and should be chosen to best suit your needs. The Apogee MQ models both have handheld meters which give you a digital readout of the PAR measurements, store data, and adjust settings using the included handheld monitor.  The Apogee SQ models are designed for direct connection to a computer using a USB cable and the PQ model works using Bluetooth for connection with your smartphone.  The Seneye monitor connects to your PC via USB and uses proprietary software, and the Neptune Systems PAR meter is only for use with a Neptune Systems Apex.

The level of accuracy you desire should also be considered along with the type of lighting you are using over your aquarium as it pertains to the various types of sensors and brands we described earlier. Choose the meter that can achieve the level of accuracy that will work for you based on the type of lighting you have.  

How To Take PAR Measurements

You know the amount of PAR your corals need to thrive and you have chosen the most ideal PAR meter for your scenario, now its time to measure the PAR inside your aquariums.

PAR grid over an aquarium
It is best to measure PAR at the bottom, middle, and top of the water column to get an idea of how the PAR changes throughout the depth of your tank. You can record those measurements onto a picture of your aquarium and save it. This way you won't forget what kind of PAR your achieving in various areas of the tank and you can place future corals appropriately.  

To get more PAR, increase the output of your lighting and for less PAR, decrease the output. When shifting the output, you don't want to change the color spectrum and you should retain the ideal spectrum settings regardless of the output level. If you're dealing with multiple color channels, adjust each channel in equal proportions to retain the ideal spectrum. 

Once you have those PAR zones recorded, you will never need to adjust your lighting again. The light settings can remain throughout the life of the aquarium and you won't ever need to measure PAR again unless you change the settings (rarely required) or get a new light.