What is PAR? It stands for Photosynthetically Active Radiation. PAR is the measure of light available for photosynthesis. You will notice optimal PAR values listed on all photosynthetic coral pages under it's Stats > Lighting Requirement section. For more info on PAR meters, watch this video:
Tip: We understand this is an expensive piece of equipment you won't need all the time. May we suggest purchasing one with your local reef club or group of hobbyist friends. This way you all can pass it around when needed.