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Calculate aquarium water volume in gallons and liters for rectangular, bow-front, cylinder, and corner tanks including substrate and displacement.
Calculate CO2 injection rate for planted aquariums from tank volume, target pH, KH carbonate hardness, and bubble rate for stable dissolved CO2.
Check tropical fish compatibility for community tanks by temperament, tank size, water parameters, and schooling needs before adding new species.
The standard guideline is 3–5 watts per gallon for temperate rooms (65–72°F ambient). Cold rooms (below 65°F) need 5–7 watts per gallon.
Heater watts = Tank gallons × 3 to 5 (adjust for room temp)Larger gaps between room and target temperature require more wattage. Tropical tanks at 78°F in a 60°F room need more power than in a 72°F room.
Adjusted watts = Base watts × (Target − Room) / 15Divide total wattage by gallons to estimate heat-up rate. Roughly 1 watt per gallon raises temperature ~1°F per hour in a standard glass tank.
Heat-up (hours) ≈ (Target − Current) / (Watts / Gallons)Updated: July 2026
Target 78°F with 4°F differential above baseline. 20 gallons × 4 watts = 80W minimum. A 100W heater provides margin and faster recovery after water changes.
16°F differential to reach 78°F. 55 × 5W = 275W base, adjusted up for cold room. Use two 150W heaters at opposite ends for even distribution and redundancy.
6°F rise to 78°F in small volume. A 50W heater is standard for 10 gallons. Consider a heater controller for precise ±0.5°F stability.
A 300W heater on a 10-gallon tank overshoots temperature rapidly if the thermostat fails. Match heater size to tank volume and add an independent controller for safety.
Direct flow past the heater thermostat causes false readings and short cycling. Position the heater in an area with gentle circulation, ideally with a small wavemaker for even distribution.
An undersized heater struggles in cold rooms; an oversized one causes dangerous temperature swings. This calculator determines ideal heater wattage from tank volume, ambient room temperature, target water temperature, and acceptable heat-up time.