PAR

What does PAR mean?

PAR (Photosynthetically Active Radiation) measures the amount of light in the 400-700 nm wavelength range available for photosynthesis. In reef tanks, PAR is the make-or-break parameter for coral and host-anemone health, expressed in micromoles per square meter per second (µmol/m²/s).

How is PAR used in aquariums?

SPS coral and host anemones generally need 250-500+ PAR at the placement; LPS thrive at 100-250 PAR; soft corals tolerate 50-150 PAR. Measured with a quantum meter (Apogee MQ-510 or equivalent) - reef LEDs at the manufacturer-stated wattage do NOT guarantee target PAR; depth, water clarity, and reflector geometry all matter.

How PAR fits the bigger picture

Understanding PAR matters because it's connected to broader husbandry decisions: lighting drives photosynthesis, coloration, and growth - get it wrong and corals/anemones bleach or recess.

Browse the Fast Aquatics care library for full husbandry tutorials covering PAR in context.

Frequently asked questions

What does PAR mean in fishkeeping?

PAR (Photosynthetically Active Radiation) measures the amount of light in the 400-700 nm wavelength range available for photosynthesis. In reef tanks, PAR is the make-or-break parameter for coral and host-anemone health, expressed in micromoles per square meter per second (µmol/m²/s). Understanding PAR matters because it's connected to broader husbandry decisions: lighting drives photosynthesis, coloration, and growth - get it wrong and corals/anemones bleach or recess.