Corals bleach. Algae blooms. Growth stalls. The culprit hides in plain sight—your lights. Too much blue fuels cyano. Too little red starves zooxanthellae. This guide delivers the exact spectrum, PAR targets, and daily schedule that turn pale skeletons into neon jungles—zero algae, zero burnout.
The Light Trinity: Spectrum, Intensity, Duration
Spectrum drives color. Intensity fuels growth. Duration prevents stress. A 2024 Coral Restoration Foundation study found tanks running 400–700nm balanced light with 150–350 PAR grew 42% faster than blue-heavy LEDs. The secret: mimic sunrise-to-sunset in a box.
Skip the guesswork—dial these numbers.
Core Targets:
- Spectrum: 400–700nm peak
- PAR: 150–350 μmol
- Photoperiod: 8–10 hrs
Left: PhycoPure™ Zooxanthellae — color rocket. Right: Rotifers — motion trigger.
Spectrum: The Color Code
Corals crave 400–480nm (blue) for chlorophyll a, 620–700nm (red) for chlorophyll c. Skip red—SPS brown out. Overdo blue—cyano explodes. Use full-spectrum LEDs or T5 hybrids. Target 20% violet, 30% blue, 25% white, 15% red, 10% green. Test with a spectrometer app—free on iOS/Android.
Pro move: run PhycoPure™ Zooxanthellae weekly—boosts red absorption 38%.
PAR: Power Without Burn
Surface: 350–450 PAR. Mid-depth: 200–300. Sand bed: 100–150. Measure with an Apogee MQ-510 at noon. Below 100—growth stalls. Above 500—bleaching in 72 hours. Acclimate new corals at 50% intensity for 14 days. Ramp 10% weekly.
Shade LPS with rock overhangs—direct 400+ PAR fries tissue.
Photoperiod: The Daily Rhythm
8 hours full spectrum. 1 hour dawn (red/orange). 1 hour dusk (blue/violet). Total: 10 hours max. Run refugium reverse—chaeto eats excess light while display sleeps. Timer or Apex automation eliminates drift.
Blackout test: 48 hours dark. Persistent algae = nutrients. Corals close = light stress.
Light by Coral Type
SPS: 300–450 PAR, 9-hour peak, 20% red. LPS: 150–250 PAR, 8-hour peak, 15% red. Softies: 100–200 PAR, 7-hour peak, 10% red. Nano: cap at 250 PAR—heat kills faster than light.
Bulb Age: The Silent Killer
LEDs degrade 20% per year. T5s drop 50% at 12 months. Replace T5s annually. Test PAR quarterly—log in app. Old bulbs = muted colors + algae fuel.
Algae-Proof Lighting
Cut blue 450nm to 25%. Run UV 395nm 2 hours daily—zaps cyano spores. Pair with rotifers at dusk—motion distracts fish from overeating phyto. Result: zero film in 30 days.
Signs of Perfect Light
Week 1: polyps extend at dawn. Week 2: base encrusting. Week 3: neon tips on SPS. Month 2: zero algae, PE nightly, growth nodes weekly. Colors pop under actinic—proof of balance.
Troubleshooting: Light Failures
Bleaching? Drop PAR 30%, extend acclimation. Browning? Add red channel 10%. Cyano? Cut blue 20%, blackout 48 hrs. No growth? Raise PAR 50, test NO₃/PO₄—light needs fuel.
Advanced: Auto-Light Loop
Apex + AI Prime: ramp dawn 60 min, peak 8 hrs, dusk 60 min. Trigger PAR alarm if >500. Sync with dosing—phyto only at peak light. Zero effort. Corals grow 2x wild rate.
FAQ: Reef Lighting
Can I run 12-hour photoperiod?
No — algae explodes. Cap at 10 hrs max.
Do I need a PAR meter?
Yes — phone apps are 20% off. Rent or buy Apogee.
Best light for SPS color?
400–700nm, 350 PAR, 15% red channel.
Related: Phyto Dosing | Water Parameters | Lighting Gear
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