What Temperature Should My Reef Tank Be?
Quick Answer
The ideal reef tank temperature is 76-78°F (24-26°C). Most coral and fish thrive in this range, though stability matters more than hitting an exact number.
The ideal reef tank temperature is 76-78°F (24-26°C). This range provides optimal conditions for most corals, fish, and invertebrates commonly kept in home aquariums. However, consistency is more important than hitting a specific number—fluctuations cause more problems than being a degree off target.
Why Temperature Matters
Reef organisms are ectothermic, meaning their body temperature matches their environment. Temperature affects:
- Metabolism — Higher temps increase metabolic rate (faster growth but more oxygen demand)
- Coral health — Too warm triggers bleaching; too cold slows growth dramatically
- Oxygen levels — Warmer water holds less dissolved oxygen
- Disease resistance — Stress from temperature swings weakens immune systems
Acceptable Temperature Ranges
- Ideal: 76-78°F (24-26°C)
- Acceptable: 75-80°F (24-27°C)
- Danger zone: Below 74°F or above 82°F
SPS corals (Acropora, Montipora) prefer the cooler end of the range. Many experienced reefers keep SPS-dominant tanks at 75-77°F to reduce bleaching risk.
Temperature Stability Tips
- Use a quality heater — Invest in a reliable heater with good thermostat accuracy
- Consider a controller — Apex or similar controllers provide backup protection
- Monitor daily — Track temperature in the ReefBay app to spot trends
- Avoid direct sunlight — Natural light causes afternoon temperature spikes
- Plan for summer — Use fans, chillers, or AC to prevent overheating
What Causes Temperature Swings?
- Heater failure or stuck-on heater (most dangerous)
- Room temperature changes (AC/heat cycling)
- Intense lighting without adequate cooling
- Power outages
- Water changes with mismatched temperature
Keep daily fluctuation under 2°F. Larger swings stress livestock and can trigger coral bleaching even within the "safe" range.
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