The best method to work out the wattage of heater required for your home aquarium fish tank is to consider the average ambient temperature of the room and work out how much extra heat will be required to increase the temperature of the water above this.
| Tank Size | Heat 5ºC/9ºF | Heat 10ºC/18ºF | Heat 15ºC/27ºF |
| 5 gal/25 L | 25 watt | 50 watt | 75 watt |
| 10 gal/50 L | 50 watt | 75 watt | 75 watt |
| 20 gal/75 L | 50 watt | 75 watt | 150 watt |
| 25 gal/100 L | 75 watt | 100 watt | 200 watt |
| 40 gal/150 L | 100 watt | 150 watt | 300 watt |
| 50 gal/200 L | 150 watt | 200 watt | two 200 watt |
| 65 gal/250 L | 200 watt | 250 watt | two 250 watt |
| 75 gal/300 L | 250 watt | 300 watt | two 300 watt |
I would always recommend using 2 heaters for your aquarium which are equal to the total wattage required. So for example if you have a 100 litre aquarium and need to heat it from 18 degrees to 28 degrees (10 degree C increase) then the table recommends using a 100W heater. I would however use 2x 100W heater. Provided you are using thermostat integrated heaters (of which most are these days) then you will not use up any more power or electricity as they wont be on for as long to heat the water. This is simply a precautionary measure in case one of the heaters fails, the secondary heater would still be capable of heating to the correct temperature, giving you time to purchase a replacement second heater.
This is purely a guide and should give a good rough estimate of what you would need for your fish tank to ensure the right temperature is maintained. It cannot hurt to have too much wattage of heat in the aquarium as they will simply turn off if the tank has reached the desired temperature.
Hidom 25w Submersible Aquarium Fish Tank Shockproof Thermostat Heater with Adjustable Temperature – Suitable for Fish, Shrimp and terrapin – Fitted with a UK Plug
Features:- Hidom Aquarium Heaters offer high performance aquarium heating for a range of tank sizes, The HT-2025 25w fish heater is recommended for tanks up to 30 litres
- High-precision temperature control system – Keep your aquarium at exactly the right temperature with this high performing, precise and reliable heater. Ideal for Tropical and Marine fish tanks
- Fully submersible design – Allows for placement anywhere in aquarium either vertically or horizontally – On/off light indicates when heater is operating
- Toughened Safety Glass – Thickened explosion-proof glass ensures any large fish, with a habit of knocking against the heater, from breaking the glass – Made to CE IP68 Standards – UK 3 pin plug
- Compact Mini Aquarium Heater – Ideal for shallow fish tanks as this heater is only 20cm in length – Package includes two strong rubber suckers with clips to secure to side of tank
New From:
£9.82 In Stock
Hidom 50w Submersible Aquarium Fish Tank Shockproof Thermostat Heater – Adjustable Temperature HT-2050 Upgraded Specification
Features:- Hidom Aquarium Heaters offer high performance aquarium heating for a range of tank sizes, The HT-2050 50w fish heater is recommended for tanks up to 60 litres
- High-precision temperature control system – Keep your aquarium at exactly the right temperature with this high performing, precise and reliable heater. Ideal for Tropical and Marine fish tanks
- Fully submersible design – Allows for placement anywhere in aquarium either vertically or horizontally – On/off light indicates when heater is operating
- Toughened Safety Glass – Thickened explosion-proof glass ensures any large fish, with a habit of knocking against the heater, from breaking the glass – Made to CE IP68 Standards – UK 3 pin plug
- Compact Mini Aquarium Heater – Ideal for shallow fish tanks as this heater is only 20cm in length – Package includes two strong rubber suckers with clips to secure to side of tank
New From:
£10.45 In Stock
Hidom Aquarium Heater 100w HT-2100
Features:- Hidom Aquarium Heaters offer high performance aquarium heating for a range of tank sizes, The HT-2100 100w fish heater is recommended for tanks up to 100 litres
- High-precision temperature control system – Keep your aquarium at exactly the right temperature with this high performing, precise and reliable heater. Ideal for Tropical and Marine fish tanks
- Fully submersible design – Allows for placement anywhere in aquarium either vertically or horizontally – On/off light indicates when heater is operating
- Toughened Safety Glass – Thickened explosion-proof glass ensures any large fish, with a habit of knocking against the heater, from breaking the glass – Made to CE IP68 Standards – UK 3 pin plug
- Compact Mini Aquarium Heater – Ideal for shallow fish tanks as this heater is only 20cm in length – Package includes two strong rubber suckers with clips to secure to side of tank
New From:
£11.95 In Stock
Hidom 150w Submersible Aquarium Fish Tank Shockproof Thermostat Heater – Adjustable Temperature HT-2150 Upgraded Specification
Features:- Hidom Aquarium Heaters offer high performance aquarium heating for a range of tank sizes, The HT-2150 150w fish heater is recommended for tanks up to 150 litres
- High-precision temperature control system – Keep your aquarium at exactly the right temperature with this high performing, precise and reliable heater. Ideal for Tropical and Marine fish tanks
- Fully submersible design – Allows for placement anywhere in aquarium either vertically or horizontally – On/off light indicates when heater is operating
- Toughened Safety Glass – Thickened explosion-proof glass ensures any large fish, with a habit of knocking against the heater, from breaking the glass – Made to CE IP68 Standards – UK 3 pin plug
- Wide Temperature range – From 16C-32C, adjustable via a simple knob on the top – Package includes two strong rubber suckers with clips to secure to side of tank
New From:
£12.43 In Stock
Hidom 200w Submersible Aquarium Fish Tank Shockproof Thermostat Heater – Adjustable Temperature HT-2200 Upgraded Specification
Features:- Hidom Aquarium Heaters offer high performance aquarium heating for a range of tank sizes, The HT-2200 200w fish heater is recommended for tanks up to 200 litres
- High-precision temperature control system – Keep your aquarium at exactly the right temperature with this high performing, precise and reliable heater. Ideal for Tropical and Marine fish tanks
- Fully submersible design – Allows for placement anywhere in aquarium either vertically or horizontally – On/off light indicates when heater is operating
- Toughened Safety Glass – Thickened explosion-proof glass ensures any large fish, with a habit of knocking against the heater, from breaking the glass – Made to CE IP68 Standards – UK 3 pin plug
- Wide Temperature range – From 16C-32C, adjustable via a simple knob on the top – Package includes two strong rubber suckers with clips to secure to side of tank
New From:
£12.90 In Stock
Hidom 300w Submersible Aquarium Fish Tank Shockproof Thermostat Heater – Adjustable Temperature HT-2300 Upgraded Specification
Features:- Thermostat Heater, Precise & Reliable temperature control
- Suitable for aquariums up to 300 litres (dependant on model choice)
- Ideal for Tropical / Marine or Freshwater
- High Quality Components – Fitted with UK 3 pin plug
- 1.5mm Extra Thick Glass – 1.5m Cable
New From:
£13.95 In Stock
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