Understanding lighting in a marine aquarium is critical if you plan on growing photosynthetic organisms. Photosynthetic Active Radiation (PAR) is “the amount / intensity of light that is in the proper spectrum for corals to utilize.”  A quantum PAR meter measures photosynthetic photon flux density (PPFD) in µmol/(m²s). This will provide a more granular scale than just low, medium, and high light descriptions.

You can adjust the light setting and place corals more appropriately with a PAR meter.  Since every aquarium is different it is best to map the latitude of the light fixture chosen and the PAR performance for each mounting point in the aquascape.

The PQ510 package includes the following:

•  AA-090 protective Neoprene Case
• AT-100 microCache Bluetooth Micro Logger
• SQ-500-SS2 Full-spectrum Quantum sensor (with a 2 meter cable)
• AM-020 Apogee PVC Sensor Platform
• Extra 2545 microCache battery

Recommended Accessory:

• AM-320 Water Submersible Sensor Wand

Software: Apogee Connect Mobile App for µCache – Model AT-100  (Android / IOS)

Assembly, Setup , and Use

The assembly was simple. Connect the sensor to the microCache logger.  Screw the sensor onto the wand and use the 3 Velcro strips to fasten the excess cable to the bar.

Install the Apogee Connect on your Android/Apple device. Follow the prompts to attach the device and define the sensor used. Make sure to “Enable Water Correction” in Settings by typing in the sensor serial number labeled on the cable. The mobile app can record the data over a period of time. The photoperiod and Daily Light Integral (DLI) can be calculated with that data.  Below are some screenshots of the Apogee Connect datalogger mobile app.

I measured my 4’x2’50 gallon shallow lagoon tank with a rebuilt Maxspect R420R 16,000K at 18″ above the water’s surface. The water level in this shallow lagoon is only 10″ deep. 300 µmol/(m²s) just under the water line, ~150 µmol/(m²s) directly under the LED pucks on the sand and ~ 50 µmol/(m²s) at the edges of the tank.

Middle of the tank directly on the sand bed near my 3 Tridacna derasas

Edge of the tank near my “Low light” adapted meat corals (Acanthophyllia deshayesiana)

Mapping these measurements in every tank allow me to move my corals around without the need to worry about light acclimation as much.

The data can be exported to a PC for further data analysis or storage. Definitely a tool for the advanced aquarist.

Pros:

• Easy to install and use
• Light and not cumbersome, being wireless
• Feature-rich Mobile App
• Easily update the firmware from the app to keep it current
• Great for assessing the effectiveness of the light fixture since even LEDs degrade over time even though they appear lit

Cons:

• Cost – ~$600 + Wand ~$70  (at the time of writing)