Coral Acclimation Light Ramp Guide: PAR Steps Over 14 Days
The single fastest way to bleach a SGD 80 acropora frag is to drop it under your full reef lighting on day one. A measured coral acclimation light ramp stages PAR exposure across 14 days so zooxanthellae adapt gradually, photosynthesis stabilises, and pigment expression intensifies rather than collapses. This protocol from Gensou Aquascaping at 5 Everton Park reflects how seasoned Singapore reefers handle frag introductions across AI Hydra, Kessil and ATI Straton fixtures.
Why Light Acclimation Matters
Coral frags spend weeks or months under shop lighting calibrated to PAR 60-120, often with a heavy blue spectrum tilt. Your display likely runs PAR 150-400 depending on coral type and depth. Dropping a low-light-acclimated frag directly into 350 PAR triggers photoinhibition, zooxanthellae expulsion and bleaching within days. The pigment collapse is reversible but takes weeks of recovery.
Measuring PAR in Your Tank
An Apogee MQ-510 underwater PAR meter at SGD 580-680 is the gold standard for mapping your reef lighting. The Seneye Reef at SGD 350 doubles as a PAR and water-quality meter. Without a meter, work from manufacturer schedules — AI Hydra 32 at 80 per cent intensity hangs roughly 30 cm above water typically delivers PAR 250 at the sand bed and PAR 400 at the upper rocks. Browse meters in the aquarium equipment range.
Day One to Three: The Bottom Zone
Place every new frag — soft, LPS or SPS — at the lowest light zone of the display, typically PAR 60-100 at the sand bed corner. Eggcrate frag racks make this easy. Polyp extension during this window indicates the coral is settling. Polyp closure beyond 24 hours signals over-stress and means the placement was still too bright.
Day Four to Seven: First Step Up
Move soft corals (zoanthids, mushrooms, leathers) to PAR 100-150. Move LPS (hammer, frogspawn, candy cane, trachyphyllia) to PAR 80-130. Hold SPS at the bottom zone PAR 80-100. Watch for tissue colour shifts — a slight darkening indicates zooxanthellae expansion in response to higher light, which is healthy.
Day Eight to Eleven: Mid-Level Light
Soft corals settle at their final PAR 100-200. LPS move to mid-rocks at PAR 130-200. SPS step up to PAR 150-200. Acroporas and montiporas at PAR 200 develop polyp extension and begin showing colour shifts toward final pigmentation. Photo-document daily — visible changes give early warning of stress before tissue loss.
Day Twelve to Fourteen: Final Placement
Acroporas and other SPS reach final placement at PAR 250-400 in the upper rockwork. Stylophora and pocillopora handle PAR 250-350. Most LPS prefer PAR 100-150 long-term and should not climb further. Hold position from day 14 onward and watch tissue thickness, polyp extension and colour over four weeks before judging success.
Spectrum Adjustment Within the Ramp
If switching from a Kessil shop tank to your Radion or AI Hydra fixture, the spectrum profile differs even at matched PAR. Run the new lighting at 60 per cent intensity for the first 7 days, then ramp upward over the next 7. Many reef controllers (Apex, Hydra app) allow custom acclimation schedules that automate the gradient.
Photoperiod During Acclimation
Reduce daily photoperiod by 1-2 hours during the first week of acclimation. A standard 8-hour blue plus 4-hour full-spectrum schedule becomes a 6-hour blue plus 3-hour full-spectrum schedule on days one to seven. Return to full photoperiod by day 14. Stock spectrum-tunable lighting in the aquarium equipment range.
Signs the Ramp Is Working
Polyp extension steady or increasing across days, tissue staying smooth without recession, colour either holding or shifting toward the species’ typical pigmentation. SPS often colour up most dramatically during weeks 2-6 post-acclimation as pigment-protective protein expression catches up to higher PAR exposure.
Signs the Ramp Is Failing
Tissue paling, polyp closure beyond 24 hours, brown jelly forming on stressed colonies, bleaching at the apex of acroporas. Drop the coral back two zones (lower light, lower flow), reduce photoperiod by 2 hours, and re-test the ramp 7 days later. Consult the water care range for emergency dip products if pigment loss accelerates.
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emilynakatani
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