Proper Goldfish Water Temp

Goldfish may seem like “easy to care for” creatures. You may even have the mentality that goldfish can be purchased (or won at a state fair) placed in a bowl with some water from the tap and fed fish flakes once in a while.

Well, sure, if you get a goldfish, stick it in a bowl with some water and only feed it fish flakes once in a while then, of course, it will be “easy to care for” because your goldfish will be dead in less than a week.

If you are thinking about becoming a goldfish owner, do your research! Prepare for your new finned friend and provide the best life you can for him. One of the most critical aspects of providing a healthy life for your goldfish is by tracking and recording the aquarium water temperature.

Why is it important to control the temperature of goldfish aquarium water?

Goldfish are a very adaptable species of fish. This means that they can usually live comfortably in an aquarium that reads 40ºF or even an aquarium that reads 78ºF.

However, that is not to say that goldfish should be residing in either of these conditions.

If the tank water is too cool, then your goldfish will swim much more slowly than he normally would, and he would show less interest in anything (including food).

If the tank water is too warm, then your goldfish can be prone to diseases, parasites and other illnesses. One of these health conditions includes Swim Bladder disease.

Swim Bladder Disease is a syndrome in which goldfish cannot swim as they normally would. This abnormal swimming will then lead to other problems including fatigue and malnutrition.

Goldfish are happiest when their aquarium water temperature falls between 65ºF and 72ºF.

Aquariums that reach the 80’s or higher become very stressed and ill.

You will likely need to scoop out your floating goldfish in a day or two of your goldfish living in such uncomfortable and dangerous conditions.

How can I control the temperature of the aquarium water?

There are various ways to control your goldfish aquarium temperature.

One thing you can do is to purchase an aquarium heater.

These heaters are specifically designed to control the temperature of the tank water. Goldfish will not need you to keep it on a very high setting.

In fact, if you hold it on a lower setting it may very well keep the tank water at a comfortable 70ºF.

Another way that you can help control the temperature is by placing your aquarium away from direct sunlight, radiators, electric floor heaters, drafts, windows, or air conditioning units.

All of these factors can cause the aquarium water temperature to rise and fall without you directly doing so.

What should I use to test the temperature of the aquarium water?

There are various types of thermometers on the market today. Any of which would provide you a relatively accurate water temperature.

The Compact Digital Aquarium Thermometer: 

These thermometers are very easy to read as they digitally display it for you on a screen. They can be programmed to read the temperature in Celsius or Fahrenheit depending on whichever one you use.

To use these devices, just attach the digital screen to the outside of your aquarium by using the provided suction cup.

The reader probe side should be suctioned to the inside of the aquarium and should be placed a few inches or so into the water.

Press the “Power” button on the digital display side and choose Fahrenheit or Celsius and watch as it reads it for you.

This type of thermometer would work very well for people with poor eyesight.

Hagen Thermometers:

There are three different varieties of the Hagen Thermometer.

You can choose from the Stainless Steel hanging thermometer; the Plastic suctioned thermometer or the Floating Glass Thermometer, which also can be suctioned.

The Stainless Steel hanging thermometer is hung on the inside of the aquarium from the edge of the tank glass and should be mostly (if not completely) covered by the tank water. The suctioned Plastic thermometer can be placed on any of the inner walls and at any depth inside the tank.  

Finally, the suctioned (or floating) Glass thermometer can be secured to an inner wall at any depth by the suction cup, or it can be free floating inside the aquarium.

These thermometers are what you might typically see in pet store aquariums and your friends’ aquariums.

They are highly recommended if you can accurately read the temperature. Many specialists will recommend a thermometer that can float inside the aquarium as these tend to have more accurate readings. However, any type should do the job.

Regardless of the style thermometer you choose, you should not worry about cost. They are all relatively inexpensive.

Of course, that does not mean that some companies do not offer a “high tech” thermometer that can run upwards of $100.

How often should I test the temperature of the aquarium water?

You want to monitor closely the temperature of your goldfish aquarium to be aware of any sudden changes. These sudden changes can significantly affect your goldfish and cause them to go into shock, become ill and on some occasions even pass away.

You should keep a goldfish journal of all of the tests you perform, water changes, the dates, and the results. While water tests and water changes may only be required every couple weeks, recording the water temperature should be done every day around the same time.

During the first few weeks to a month of having your aquarium up and running, you should check the temperature of the water a couple of occasions throughout the day.

This will let you know whether or not you need to make adjustments.

What should I do if I plan to breed my goldfish?

Goldfish instinctively begin producing when the winter water temperature starts to rise in the spring. If you intend on breeding your goldfish, you will need to replicate these water conditions.

Start by slowly lowering the aquarium water temperature (no more than 2ºF per hour).

Your ending “winter” temperature should read between 50ºF and 55ºF.

If you allow your goldfish aquarium water temperature to become any lower than that, it can cause your goldfish to go into shock as well as become inactive.

Then, after the “winter months” are over, begin raising the water temperature slowly (no more than 2ºF per hour). This should continue until the temperature reads normal water temperatures (68ºF to 75ºF).

Your goldfish should instinctively breed during this process as it closely replicates the winter and spring water temperature change.

What options do I have if I do not want my goldfish to produce?

If you do not wish for your goldfish to produce, then you will need to purchase a heater and keep it at a low temperature (or whichever setting allows the tank water to remain between 68ºF and 75ºF).

It is essential that the temperature never dramatically rise or fall regardless of whether or not you are planning to breed.

Dramatic temperature changes result in your goldfish going into shock, becoming ill, and on some occasions passing away.

A steady water temperature for non-breeding goldfish aquariums should be your goal.

What can cause a temperature fluctuation in my goldfish aquarium?

1. Purchasing an aquarium heater and not setting it to a constant If you allow your heater to run without controlling how warm or how cold it keeps the water then this will ultimately produce water temperatures that are inadequate for goldfish and can result in illness or death.
2. Placing your aquarium near a window or door. Windows and doors are potentially very harmful to goldfish aquariums. They allow direct sunlight to shine into your aquarium causing the temperature to rise higher than your goldfish can handle. The direct sunlight can also create the perfect environment for parasites and harmful bacteria to produce. On the other hand, windows and doors often have drafts that can be particularly detrimental to goldfish during the cold winter months.
3. Placing your goldfish aquarium near electric floor heaters, AC units, or radiators. These devices may create a more comfortable home for you, but they create a critical habitat for your goldfish. AC units will cause the aquarium water to be too low, and radiators or electric floor heaters can cause aquarium water to be too high.
4. Forgetting to include an air source for your goldfish aquarium. Goldfish (and all fish) get their oxygen from the oxygen in their water. If their aquarium water is too warm, then there will be less oxygen for them, thus making it difficult for them to breathe. Also, overpopulating your aquarium will reduce the amount of oxygen in an aquarium as well. To avoid a lack of oxygen, only supply your aquarium with one goldfish per 20-gallons of water. Control the water temperature and keep is at a steady 68ºF to 75ºF. Finally, you can (and should) provide some type of air supply inside the tank. You can choose an air pump, air stone, or another aeration device to ensure proper oxygenation of the water.