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Water Temperature Range for Goldfish: Set It & Forget It

While many people don’t pay attention to the temperature of their goldfish tanks, I’ve found that it’s actually one of the most important factors of all. Goldfish require a specific temperature.

Quick Answer

Goldfish can survive in a wide temperature range anywhere from 55 degrees to 80 degrees Fahrenheit. However, the ideal temperature range is somewhere between 65 and 75 degrees Fahrenheit. Ideally, the water temperature for goldfish should be somewhere around 70 degrees Fahrenheit. 

Keep reading to find out everything there is to know about the water temperature range for goldfish and why it’s so important.

The Right Water Temperature for Goldfish: Keeping Them Healthy

The water temperature for goldfish should be somewhere on the cooler side, ideally around 70 degrees Fahrenheit. However, what happens if the water is too hot or too cold?

After all, if goldfish have an ideal temperature range, it means that if they don’t live in this temperature range, that there will be issues. 

Goldfish in aquarium with green plants

Indeed, this is true. Let’s take a look at some of the most common issues that your goldfish may face if it is living in temperatures that are either too hot or too cold.

What If the Water Is Too Hot?

Goldfish are cold water fish, which means that living in temperatures that are far too warm for them can be disastrous for their health. Let’s take a quick look at the issues that your goldfish will face if the water is too warm.

  • If the water is too warm, it will raise the metabolism of your goldfish. This means that the goldfish will end up requiring more oxygen and food. This in itself can lead to a variety of digestion issues, it may lead to you overfeeding the fish, and could eventually lead to death. At the very least, a fish that eats too much also creates too much waste, which can lead to poor water quality.
  • Speaking of dissolved oxygen, remember that goldfish need to breathe as well. The issue is that if the water is too warm, it won’t be able to hold on to enough dissolved oxygen for your goldfish to breathe. If you notice your goldfish gasping for air at the surface, this is exactly what is going on. Oxygen deprivation can of course lead to death if the issue is not taken care of.
  • Warm waters are also problematic because they can encourage the growth of various parasites, bacteria, and organisms. These may all in their own way infect your fish and cause serious health issues, and eventually death.
  • Living in temperatures that are too warm, both because of the temperature itself and because of all of the other issues we have discussed so far, can cause massive amounts of stress to your goldfish. Eventually, this may lead to death. Furthermore, extreme temperature fluctuations can also cause heat shock in goldfish, which can also quickly cause their demise.

Also interesting: How Big Can Goldfish Get? Check it out now!

What If the Water Is Too Cold?

Just like if the water temperature is too hot for goldfish, being too cold is an issue as well. Let’s take a look at what might happen if the temperature is too low for your goldfish.

  • If the temperature is too low, your goldfish might just become lethargic and sluggish.
  • A goldfish living in cool water will also have a much slower metabolism. This means that they won’t eat as much or move as much. If the temperature drops below a certain mark, your goldfish might stop eating altogether, which as you could probably tell, will be very problematic.
  • Speaking of eating, if the water is far too cold for your goldfish, it may slow down its digestive system and metabolism to the point where it might cause problems with food compaction and nutrient absorption. These are fairly big issues that can lead to death.
  • In terms of death, if the water is too cold, it may cause cold stress or even hypothermia in your goldfish. As you can probably tell, these are also life-threatening conditions.

Using the Right Equipment to Maintain Stable Tank Temperatures for Goldfish

If you expect to keep your goldfish tank within the proper temperature range for your fish, then you’ll need a couple pieces of equipment. The simple reality is that maintaining a steady temperature inside of an aquarium is 100% impossible if you don’t have the right tools.

After all, if you don’t have tools to monitor the temperature, how are you supposed to know what the current temperature is? Furthermore, without a heater, how are you supposed to raise the water temperature if it is too cold?

On that note, let’s keep in mind that generally speaking, the issue will usually be that the water is too cold, not too warm. Unless you live in a tropical environment where the ambient temperature is regularly 80 degrees Fahrenheit, then the issue will be keeping the water warm enough.

So, first and foremost, you’ll want to invest in a decent aquarium thermometer. A good aquarium thermometer will allow you to monitor the water temperature at all times. 

There are some pretty good models out there, with those that have a temperature probe that is inserted right into the aquarium water being the most accurate of all.

However, there are also others that measure the water temperature through the glass, and these are a bit more visually appealing and affordable. 

I recommend doing some research into the different types of aquarium thermometers before making a choice. Whatever the case, you want something that is rated as being very accurate, which also provides you with real time temperature updates.

Of course, being aware of the temperature is only half the battle, but controlling it is the other half. 

For this reason, you need to invest in a high-quality aquarium heater. I recommend investing in something that allows you to adjust the temperature as needed, as well as something that comes with its own thermostat.

This way, you can set the temperature on the aquarium heater, and the unit will do the rest. It will continuously monitor the water temperature on its own and turn itself on and off depending on the current temperatures. 

If the water is too cold, a heater with a thermostat can automatically recognize this, turn on, and heat up the water to the desired temperature.

How to Maintain Stable Aquarium Temperatures for Goldfish

Even if you have a thermometer and a heater, maintaining a stable temperature can be a challenge inside of an aquarium. However, there are some valuable tips that I can provide you with, so that it will make it much easier for you to keep a constant temperature for your goldfish.

  • First and foremost, the location of your goldfish tank really does matter. More than anything else, you want to keep the tank out of direct sunlight. The issue with direct sunlight is that it will quickly heat up the aquarium water. Sitting in direct sunlight can heat up the water by a good few degrees within a couple of hours, and this kind of temperature fluctuation is terrible for your fish. Furthermore, once the sun goes away, the temperature will once again drop, which is also not good. Being exposed to too much sunlight may also cause algae growth to occur.
  • At the same time, you also don’t want to keep your goldfish tank in an area that is exceedingly drafty or windy. Wind will cool down the water very quickly. Although it might not seem like a small breeze is a big deal, air movement and circulation can reduce water temperatures quite drastically, and this is something that you need to avoid.
  • Furthermore, although some people may be tempted to keep their aquariums in the dark, seeing as I just said that it should not be exposed to direct sunlight, this is also not ideal. Your aquarium should be kept in a location that is fairly brightly lit, but just not in direct sunlight. If your aquarium is constantly in the dark, maintaining a somewhat warm temperature will be difficult.
  • To help maintain steady water temperatures for your goldfish, also consider getting a hood or lid for the top of your aquarium. This will help prevent water evaporation and it will help keep temperatures steady as well.
  • Although this is not something that many people know about, a good trick here is to increase or decrease the amount of water flow or water circulation in the tank to maintain constant temperatures. The more water movement there is, the faster the heat will dissipate, and vice versa. Therefore, if you find that your goldfish tank is always too hot, increasing the amount of water movement may be the solution.

Wondering what size tank is suitable for goldfish? Read this page to learn everything about the best tank size!


As you can see, maintaining the ideal water temperature range for goldfish is really not all that difficult. As long as it doesn’t drop below 65 degrees Fahrenheit or rise above 75 degrees Fahrenheit, your goldfish should be perfectly fine.

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