Calculate the required cooling capacity (BTU/hr) and recommended HP for your aquarium chiller. Accounts for sunlight, lighting type, and lid coverage.
Enter your tank volume, ambient (room) temperature, and target water temperature. A chiller is needed when the ambient temperature exceeds the target. The larger the temperature difference, the higher the cooling capacity required.
Tank location (direct sunlight, indirect light, no sunlight), lighting type (LED, T5, Metal Halide), and lid coverage all affect the heat load. Direct sunlight and metal halide lighting significantly increase cooling requirements.
It is recommended to choose a chiller one size above the calculated HP. Install the chiller near the tank with adequate ventilation. Using a lid helps improve chiller efficiency by reducing heat exchange with the room.
If summer water temperatures consistently exceed 28°C in a freshwater tank, 26°C in a planted tank, or 27°C in a reef tank. Cold-water species (axolotls, goldfish, salmonids) need cooling year-round if room temperature stays above 22°C.
Use the calculator's recommended HP, then bump up one size for safety. Undersized chillers run constantly, wear out faster, and never reach target temperature on hot days. A slightly oversized chiller cycles less and lasts longer.
In a well-ventilated area away from the tank — chillers exhaust hot air. A separate cabinet or adjacent room is ideal. Leave at least 30 cm of clearance on all sides. Sumps make chiller plumbing simpler than in-line setups on display tanks.
Yes. A 1/4 HP chiller exhausts roughly 700–1000 W of heat into the surrounding air while cooling the tank. In a small enclosed room this can raise ambient temperature noticeably, which then makes the chiller work harder. Vent if possible.
Fans use evaporative cooling and can drop water temperature 2–4°C — enough for borderline situations. They greatly increase evaporation (sometimes 5–10× normal), which means heavier top-off duties and salinity drift in marine tanks. Fans are cheap insurance, not a chiller replacement.