Pets

What Size Aquarium Heater Do You Need?

Built by Kevin Glover · @gloverbuilds · Verified formula

Calculate the right heater wattage for your fish tank based on volume and room temperature.

📅 Updated April 2026 ✅ Formula verified 📖 4 min read 🆓 Free · No sign-up

In this article

Sizing Your Aquarium Heater
Heater Safety

Règle

1W/L si écart <5°C avec l'ambiance. 1,5W/L pour 5-8°C. 2W/L pour >8°C. Aquarium tropical de 200L (objectif 26°C, ambiance 20°C) : 200 × 1,5 = 300W. Pour plus de 300L : deux chauffages pour distribution uniforme et sécurité.

Sécurité

Un chauffage bloqué en position « on » est la cause #1 de mortalité par équipement. Utilisez toujours un thermostat externe comme sécurité (15-30 €).

⚡ CalcWolf Insight

A sudden temperature drop of 5°F+ can trigger Ich (white spot disease) in tropical fish — the most common aquarium disease. A reliable heater with a temperature controller is cheaper ($40-60 total) than treating a tank full of sick fish ($20-40 in medication plus potential fish losses). Prevention is always cheaper than cure in fishkeeping.

Frequently asked questions

Combien de watts ?▾

1W/L pour faible écart. 1,5W/L modéré. 2W/L grand écart. 200L tropical : 200-300W.

Un ou deux chauffages ?▾

Plus de 300L : deux. 100-300L : un avec thermostat externe.

✓ Math logic verified against primary sources → See our verification process

Kevin Glover · @gloverbuilds

Founder, CalcWolf · GLVTS · Blickr

All formulas sourced from primary references — IRS publications, peer-reviewed research, and official standards. Results are tested against independent reference calculators before publishing. Rates and brackets updated when official sources change. Editorial policy →