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Do Goldfish Need a Heater? Spend Your Money Wisely!

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Something that I’ve realized is that there seems to be a whole lot of confusion about whether or not a goldfish needs a heater, a topic that I’m about to tackle right now.

Goldfish require the water temperature to be between 65- and 75-degrees Fahrenheit, or between 18 degrees and 24 degrees Celsius. This means that generally speaking, goldfish do not need a heater unless the ambient temperature is consistently lower than 65 degrees.

That said, there are also other considerations to keep in mind here. Keep reading to find out if your goldfish needs a heater. 

Ideal Temperature for Goldfish

In the opening paragraph, I already mentioned how goldfish require a water temperature between 18 and 24 degrees Celsius or between 65 degrees and 75 degrees Fahrenheit. While this is true, what is also important to consider is the stability of the water temperature.

You don’t want the water being 65 degrees one day 75 degrees the next day, as this can cause severe health issues. A consistent water temperature is very important to maintain.

Therefore, although goldfish may not necessarily require a heater to keep the temperature above their required minimum, they may require a heater to keep the water temperature consistent. 

Inconsistencies in water temperatures can cause health issues, as we are about to discuss below.

On that note, there are some types of goldfish, such as fancy goldfish for instance, which are fairly sensitive to temperature changes.

For these varieties especially, a dedicated cold water aquarium that is insulated to prevent temperature fluctuations may be your best bet. Read more about goldfish tank requirements right here! 

What Happens if the Temperature is Too High?

One thing I want to touch on here is what happens when the temperature is either too high or too low for your goldfish. Let’s first figure out what might happen if the water temperature is consistently too high for your goldfish.

·       The warmer the water is, the less dissolved oxygen it can hold on to. Therefore, if the temperature is significantly high, the dissolved oxygen levels in the water may become too low for your goldfish to survive, which ultimately can lead to oxygen deprivation and death.

·       If the temperature in the aquarium is too high, it can also cause your goldfish’s metabolism to go through the roof, which then means that they require more food and oxygen. This can eventually lead to digestion issues, potential overfeeding, and more.

·       High water temperatures are also not ideal because they encourage the growth of a variety of harmful bacteria, parasites, and other organisms, which can in their own ways lead to your goldfish developing a variety of diseases.

·       Overall, living in temperatures that are too high can cause your goldfish great stress, weaken their immune system, make them more susceptible to disease, puts an increased strain on their organs, and ultimately decreases their lifespan.

·       Remember that sudden exposure to extreme temperatures, especially if there is a big temperature fluctuation, can cause heat shock in goldfish, which can very quickly lead to death.

What Happens if the Temperature is Too Low?

Just like there may be issues if the water temperature is too high for your goldfish, there are also issues that may arise if the temperature is too low. Let’s take a quick look at what happens if your goldfish is kept in temperatures that are below the ideal.

·       At the very least, goldfish that are kept in cool waters will become sluggish, start swimming slower, and show less activity in general. They’ll probably start spending more time at the bottom of the tank and just be really lethargic.

·       One of the biggest effects that cold water has on goldfish is that it will reduce their metabolism, which leads to decreased activity and decreased appetite. If the temperature drops way too low, goldfish may stop eating totally.

·       If the water is too cold, it can also slow down the digestive system of your goldfish to the point where it can cause problems with nutrient absorption and food compaction.

·       If nothing else, cold waters can lead to hypothermia and a risk of cold stress. Cold stress can be life threatening if not taken care of right away.

How to Maintain Stable Temperatures in Aquariums for Goldfish

Now that we know what the ideal temperature for goldfish is, and what happens if the water is either too hot or too cold, let’s figure out how you can maintain a stable temperature in the aquarium.

1. Use an Aquarium Thermometer

One of the first things that you should always do whenever you get an aquarium is to purchase a good aquarium thermometer. 

If you expect to maintain an ideal temperature in your aquarium for your goldfish or any other fish in general, knowing the temperature is the first step.

Therefore, I recommend investing in a relatively high-quality aquarium thermometer that will provide you with constant updates and precise readings as to water temperature. 

You simply can’t adjust the temperature in your goldfish tank if you don’t know what it is to begin with.

2. Use an Aquarium Heater

To address the main point of the day: although your goldfish probably doesn’t need a heater in terms of maintaining a minimum temperature, it will likely need a heater to maintain a consistent temperature.

It is likely that the ambient temperature in your home is more than enough to keep the water above 65 degrees Fahrenheit, but remember that you also need to keep the temperature very stable.

Therefore, investing in a decent aquarium heater that has a thermostat built into it is a good idea. 

This will allow you to maintain a steady water temperature, such as an even 70 degrees Fahrenheit. In general, using a water heater of this nature is really the only and best way to maintain consistent temperatures.

On that note, you also want to maintain the aquarium heater on a regular basis. If the heater is damaged or malfunctioning, it may not heat the aquarium as required, or may even lead to very dangerous temperature swings. 

I really can’t stress enough how important it is to invest in a high-quality heater, as low quality models may do more damage than they do good.

On the topic of aquarium heaters, you do really want to go for something that is fully adjustable in nature. 

The reason for this is because it is likely that you live in an area that doesn’t see consistent temperatures. You like we have a summer and a winter, which will affect indoor temperatures as well. 

To account for these seasonal changes in temperature, you need a heater that is adjustable.

3. Insulate the Aquarium

To maintain constant temperatures in your aquarium, another great idea is to insulate it. To insulate your aquarium, use a hood or aquarium cover that will help keep heat in and prevent heat loss. You also want to ensure that any gaps or openings are sealed very well.

This will help keep the temperature at a stable minimum, while also helping to save you money. Remember that the more your aquarium heater has to run, the more money it will cost you.

Therefore, allowing your aquarium to retain heat by adding a hood into the equation is a great idea. Not only does it help maintain stable temperatures, but also helps you save money.

4. Location, Location, Location!

One of the biggest mistakes that many people make is placing their aquarium in the wrong location. First and foremost, you never want to place your aquarium in an area that is exposed to direct sunlight. 

If your aquarium is exposed to direct sunlight, when the sun shines on it, it will greatly increase the temperatures, and then when the sun goes away, the temperature will rapidly drop.

This is the exact kind of temperature fluctuation that you absolutely need to avoid at all costs for your goldfish tank.

Furthermore, you also want to avoid any area that has a lot of drafts and is very windy. If your tank is located in a windy area, whenever it is windy, the tank will cool down. It will then heat up when the wind goes away. This is another issue that can lead to big temperature fluctuations.

However, you also don’t want to keep the aquarium in a location such as the basement that is exceedingly dark at all times. Keeping your aquarium in a room that is not drafty, and keeping it in a well-lit area, but not in direct sunlight, is what you need.


The bottom line here is that strictly speaking, your goldfish likely does not require a heater. 

If you live in an area of the world that has consistent temperatures, or if you just have consistent indoor temperatures, then you might not need one. 

Just remember that the minimum temperature needs to be 65 degrees Fahrenheit, with the maximum being around 75 degrees. 

As long as you can maintain consistent temperatures within this range, a heater may not be 100% necessary.

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