Lighting for Corals: PAR for SPS, LPS and Softies
Light is food for most corals. Getting the intensity right is one of the biggest factors in coral color and growth, and the best way to measure it is PAR.
What is PAR?
PAR stands for Photosynthetically Active Radiation. It measures the amount of usable light reaching a spot in your tank. PAR drops quickly with depth and distance from the light, so a coral at the bottom gets far less light than one near the top.
PAR ranges by coral type
| Coral type | Typical PAR | Where to place |
|---|---|---|
| Mushrooms | 50 to 150 | Sand bed or low rockwork |
| Zoanthids and soft corals | 100 to 250 | Low to middle rockwork |
| LPS (hammers, chalices) | 75 to 200 | Low to middle rockwork |
| Montipora and easier SPS | 150 to 300 | Middle to upper rockwork |
| Demanding SPS (Acropora) | 250 to 400+ | Upper rockwork |
These are general ranges. Individual corals vary, and a coral that's open, colorful and growing is the best sign its light is right.
Spectrum
Reef lights lean heavily toward blue, which corals use efficiently and which brings out fluorescent colors. A full-spectrum LED with strong blue and some white light works for most mixed reefs.
Photoperiod
For a beginner mixed reef, a 12-hour schedule with a 2-hour morning ramp-up, 8 hours of peak light, and a 2-hour ramp-down keeps corals comfortable without encouraging algae.
Acclimating to new light
Corals bleach when light increases too quickly. When you add a new coral, install a new light, or raise intensity, start lower and increase over 1 to 2 weeks.
Measuring PAR
A PAR meter gives you exact readings at different spots in your tank. Many local reef clubs and stores lend or rent them. Without one, start corals low and move them up based on how they respond.
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