Do Goldfish Need A Heater?
The answer depends on the type of goldfish you have, where you live, and whether or not you can maintain a constant temperature without using a heater.
For single-tail varieties like common, comet, and shubunkin goldfish the optimum water temperature range is 64°F to 70°F (17.5°C to 21°C), which can usually be maintained without a heater.
For fancy goldfish, the optimal range is 68°F to 74°F (20°C to 23°C), so a heater can be useful to help maintain the ideal temperature.
If you’re struggling to maintain a consistent water temperature for your goldfish, using a submersible aquarium heater will alleviate this issue.
Make sure you choose a heater with an adjustable thermostat and increase the temperature slowly so you don’t stress your fish leaving them susceptible to illnesses.
I’ve left details on how to choose a heater and the one I use and recommend further down.
5 Benefits of Using a Heater in Goldfish Tanks
Using a heater for your goldfish can have significant benefits, especially for fancy goldfish in cold climates.
1. Stable Temperature
Goldfish prefer a stable environment, much like people enjoy a comfortable living space with a consistent temperature.
By maintaining a steady temperature in their tank, goldfish thrive and can avoid the stress that comes with fluctuating conditions, leading to a more relaxed and natural behavior.
2. Enhanced Metabolism
A consistent, ideal temperature can positively affect your goldfish’s metabolism.
This means they’re more likely to eat the proper amount and maintain good health if they are fed a quality varied diet.
3. Better Immunity
Sudden temperature changes can weaken their immune system, making Goldfish more susceptible to illnesses.
A consistent temperature helps to keep their defenses strong, reducing the risk of disease and allowing them to live a healthier life.
4. Promotes Growth
For younger goldfish, a constant temperature is vital for steady growth.
It allows them to develop at an ideal rate, ensuring they reach their full size and color potential without the stress that can come from an unstable environment.
5. Increased Activity
Goldfish are more active and energetic when they have the ideal tank temperature.
Although they are considered cold-water fish, the temperature can get too cold for them. If it drops and stays below 50 degrees Fahrenheit (10°C) your goldfish may enter a state called torpor to conserve energy.
Although goldfish can handle this short term (over Winter), it isn’t good for their health long-term.
How To Choose & Setup a Heater in a Goldfish Tank
The things to consider when choosing a heater for your goldfish tank are:
1. Size of Tank
Heaters are available in various wattages, and you need to get one that is suitable for your goldfish’s tank size.
I’ve made the chart below to help you with this.
| TANK SIZE | WATTAGE REQUIRED |
| 20 Gallons | 50 Watts |
| 30 Gallons | 100 Watts |
| 65 Gallons | 200 Watts |
| 100 Gallons | 300 Watts |
2. Choose a Safe & Reliable Heater
A good quality submersible heater will have a thermostat, thermometer, guard, and indicator light.
These features ensure consistent and accurate temperature control and protect your fish from potential injury or burns.
I highly recommend the Fluval E Series heaters, it’s the only heater I now use (after trying many!).
For Up To 30 Gallons  | For Up To 65 Gallons  | For Up To 100 Gallons  |
4.4 | 4.4 | 4.4 |
As an Amazon associate, I earn from qualifying purchases. This is at no additional cost to yourself. | As an Amazon associate, I earn from qualifying purchases. This is at no additional cost to yourself. | As an Amazon associate, I earn from qualifying purchases. This is at no additional cost to yourself. |
3. Place the Heater Near the Filter Output
For maximum efficiency, place the heater near the filter output to achieve the best heat distribution and avoid the ‘LF’ (low flow) warning.
This helps circulate the heated water providing a stable temperature throughout the tank.
You should also tilt the heater at a 45° angle to stop it from switching on and off over and over again as the warmer water rises and flows over the sensor.
This saves a ton of wear and tear on the internal components meaning you don’t have to replace items as often.
If you have a large goldfish tank setup it can be beneficial to have 2 smaller heaters at opposite ends, to help distribute the heat more evenly, place the 2nd heater near an airstone to help circulate the heat.
4. Use an Air Pump
Goldfish need a lot of oxygen, and warmer water holds less oxygen than cooler water.
A goldfish laying still on the tank bottom could be a sign of having low oxygen levels in the water.
Using an air pump causes water surface agitation that allows harmful gases to escape and fresh oxygen to enter.
UL certified aquarium air pump
Available in various sizes to suit tanks from 2 gallons to 100 gallons
Patented dome shape, suspended motor, and sound-dampening chambers for quiet operation
Less than 40 dB when running
6 foot power chord
- Very quiet
- Easy to setup
- Check valve included
- Increases oxygen levels in the water
- Tubing not included - 1/8" required
Outdoor Pond Goldfish
During colder months goldfish in outdoor environments can enter a semi-hibernation state called torpor if temperatures drop and stay below 50 degrees Fahrenheit (10°C). This enables the fish to conserve energy and survive in the wild when food is scarce.
If your pond freezes over and your goldfish enter this state, you’ll need to make sure there is some aeration in the pond to allow gas exchange.
This allows harmful gases to escape and oxygen to enter the pond.
The Tetra Pond De-icer is ideal for ponds of 150 square feet or larger surface area.
- 15 foot power chord
- Works down to -20°F (-28.8°C)
- Looks natural
- 3 year warranty
- Not recommended for ponds below 150 square feet of surface area - manufacturer information
Closing Thoughts on Do Goldfish Need a Heater…
So, while goldfish don’t ‘need’ a heater like tropical fish do, they do need their water to stay within a safe and stable range.
Some goldfish can benefit from having a heater in their tank, particularly an indoor aquarium with fancy goldfish.
- For single-tail goldfish like a common, comet, and shubunkin the optimum water temperature range is 64°F to 70°F (17.5°C to 21°C).
- For fancy varieties, like the fantail goldfish, the optimal range is 68°F to 74°F (20°C to 23°C).
If you are going to get an aquarium heater for your goldfish, make sure you buy a heater with an adjustable temperature, so you can create the perfect environment for your pet goldfish.
Check out the aquarium health section for more guides like this to keep your aquarium in tip-top shape.
