A water heater for a fish tank will keep your aquarium at a constant and comfortable temperature for your angelfish. Some aquarists feel that it’s better to choose a lower wattage heater so that if the contacts malfunction and permanently close, the water won’t become overheated. Others feel that choosing a heater on the higher end of the wattage output, it won’t overwork the heater and keep water warm in instances of abnormally cool weather. Both have valid reasons for their views.
How to Choose the Best Aquarium Heater
Choosing the correct heater for a tank depends on two things. Aquarium size and the temperature difference between the coldest ambient room temperature, and the tank temperature. Angelfish live in a temperature range of 75 – 82 degrees and prefer closer to the 80 degree range. The smaller the temperature variation, the lower wattage heater needed. The following list gives the temperature differential between ambient and tank temperatures for the proper heater wattage for the aquarium size. Most aquarium heater manufacturers make the same model in a variety of wattages to accommodate different tank sizes and conditions.
| Fish Tank Size | Desired Temperature Increase | Watts You Need | Heater Recommendation |
|---|---|---|---|
| 5 gallon (25 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 25 50 75 | Jager Fish Tank Heater |
| 10 gallon (50 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 50 75 75 | Jager Fish Tank Heater |
| 20 gallon (75 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 50 75 150 | Aqueon Pro Heater |
| 25 gallon (100 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 75 100 200 | Aqueon Pro Heater |
| 40 gallon (150 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 100 150 300 | ViaAqua Aquarium Heater |
| 50 gallon (200 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 150 200 Two 200-watt heaters | Pro Heater |
| 65 gallon (250 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 200 250 Two 250-watt heaters | Pro Heater |
| 75 gallon (300 liter) | 9 degrees F (5 degrees C) 18 degrees F (10 degrees C) 27 degrees F (15 degrees C) | 250 300 Two 300-watt heaters | Aquatop 300-watt Aquarium Heater |
Aquarium Heater Features to Look For
Aquarium heaters offer a variety of features.
- An adjustable aquarium heater allows raising or lowering the temperature to adjust the tank temperature with and adjustable dial.
- Others have shatterproof glass to protect against breakage. Shatterproof glass is an excellent safety feature on this model.
- Most offer a light to indicate if the heater is or off.
- Some are fully submersible and will shut off if the water level becomes too low.
- Aquarium heaters with a visible temperature setting is a nice feature. However, these aren’t always accurate and it’s prudent to check water temperature against a thermometer and adjust the heater accordingly. When checking temperature with a thermometer, keep it as far away from the heater as possible.
- A dial on the top of the heater is the normal way to adjust the temperature. The visual display has a range between temperatures, so it’s advisable to check with a thermometer to get a more accurate reading.
- High end aquarium heaters may use a digital display to show water temperature. The Fluval E samples the water temperature rather than air in the tube to obtain a more accurate reading of the actual water temperature.
All aquarium heaters do the same thing, some more precisely and accurately than others.