SPS coral coloration is driven by zooxanthellae density (browns), pigment proteins (greens, blues, purples, reds), and lighting spectrum. Stable nutrients + high blue PAR drive bright colors.
SPS coloration is the holy grail of reef-keeping. Zooxanthellae: brown algae symbionts inside coral tissue. Provide energy via photosynthesis but make corals brown when too dense. Pigment proteins: 6+ distinct pigment families. GFP (green fluorescent protein) - greens. CFP (cyan) - blues. BFP (bright blue). RFP (red). YFP (yellow). Pocillin (pink). All produced by the coral itself, not algae. Drivers: 1) high blue PAR (450nm, 405nm) stimulates pigment protein expression. 2) low nitrate + low phosphate (under 5 ppm + 0.05 ppm) starves zooxanthellae - reduces brown. 3) ultra-stable alkalinity (8.5-9.0 dKH within 0.3 dKH variance). 4) trace element supplementation (iron, manganese, zinc, iodide) - ICP testing essential. 5) genetic - some Acropora colored brilliantly under any condition; others always stay tan. Caveat: too lean on nutrients = pale + bleaching. Sweet spot is 1-3 ppm NO3 + 0.02-0.05 ppm PO4. Color reference: Tropic Marin Pro Reef + ICP-OES quarterly testing + AI Hydra/Radion blue-heavy spectrum.
Reviewed by the Fast Aquatics husbandry team · Updated May 2026
SPS coral coloration is driven by zooxanthellae density (browns), pigment proteins (greens, blues, purples, reds), and lighting spectrum. Stable nutrients + high blue PAR drive bright colors. SPS coloration is the holy grail of reef-keeping. Zooxanthellae: brown algae symbionts inside coral tissue. Provide energy via photosynthesis but make corals brown when too dense. Pigment proteins: 6+ distinct pigment families.
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