What Is The Ideal Temperature For A Tropical Fish Tank?

The ideal temperature for a tropical fish tank is generally between 75°F and 80°F (24°C to 27°C). However, it’s important to research the specific temperature requirements of the tropical fish species you plan to keep in your tank.

Different species may have slightly different temperature preferences, so it’s important to provide the appropriate temperature range to ensure the health and well-being of your fish. Maintaining a stable and suitable water temperature is key for the overall success of your tropical fish tank.

Temperature for a Tropical Fish Tank

Freshwater Fish: Tropical Vs Coldwater

Freshwater fish are categorized into two types: tropical and coldwater. Tropical fish thrive in waters with temperatures above 20 degrees Celsius (or 68 degrees Fahrenheit) year-round. On the other hand, coldwater fish, like goldfish, are considered temperate fish and prefer waters that are typically 10-20C (50-68F) year-round. Waters below 10C (50F) year-round are referred to as polar.

It’s important to note that not all tropical fish require the same temperature range. They can be further divided into those that prefer low 20s, mid-20s, and high 20s Celsius. For example, species like the Redline Torpedo Barb and Sahyadria denisonii are best kept in water ranging from 20-25C (68-78F). On the other hand, Discus fish require much higher temperatures, with 28C (84F) being the optimum temperature.

In the UK, some tropical fish species, such as White Cloud Mountain minnows and Zebra danios, can be considered temperate and can be kept in unheated fish tanks year-round. However, it’s essential to research your specific fish species to ensure they are kept in the appropriate temperature range for their well-being.

How Water Temperature Affects Fish

Water temperature greatly affects fish as they are poikilothermic, meaning their body temperature is the same as the water they swim in. Different fish have different temperature ranges they can tolerate, with their optimum temperature usually being around 25C or 78F. However, they can withstand some variation, such as 20C or 68F during transportation or power outages, and up to 30C or 86F in a heatwave.

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It’s important to avoid long-term exposure to temperatures outside of their optimum range as it may be detrimental or fatal to the fish. Additionally, warm water holds less oxygen than cold water, so if the water temperature rises, it’s crucial to increase aeration to ensure the fish have enough oxygen. Insufficient oxygen levels can be harmful to the fish even before temperature-related issues.

Different Types of Tropical Fish Water Temp

Keeping your tropical fish aquarium at the right temperature is essential to ensure a healthy and thriving environment. The water temperature should not be too hot or too cold – it should be just right. You want the water to feel comfortable to the touch and if you see ice forming on top, there’s a chance that it’s too cold.

Tropical Fish Temperature Chart:

Fish SpeciesTemperature (Celsius)
Goldfish68-74° F (20-23º C)
Tetras75-80° F (23-27º C)
Guppies72-78° F (22-25º C)
Barbs68-79° F (20-26º C)
Betta78-80° F (25-27º C)
Cichlids78-82° F (25-28º C)

Measuring Tropical Fish Water Temp

Keeping track of the water temperature in your freshwater aquarium is vital for the health of your tropical fish. Luckily, there are a few options available to measure and monitor tropical fish water temperatures.

For instance, floating thermometers roam the tank constantly to provide you with an accurate reading. Alternatively, you can use an adhesive thermometer that can be placed on the glass front of your tank for easy monitoring. Or if you prefer, you can even opt for a submersible thermometer that can be suction cupped to the interior glass wall of your aquarium.

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No matter which method you use, just make sure it’s not placed near a window or door where drafts might affect its readings. Additionally, don’t leave it somewhere that receives direct sunlight as this will throw off your results as well. With these simple tips in mind, measuring the humidity level of your tropical fish’s environment will be a breeze!

How To Check Your Fish Tank Temperature Without A Thermometer

While it can be difficult to tell the exact temperature of your fish tank without a thermometer, there are still ways to get a general idea. One option is to use your finger – try placing it in the water and seeing how it feels. Different people may experience different temperatures- for example, the same water might feel warmer in cold Fall weather than it does when it’s hot out in the middle of summer.

Unfortunately, this isn’t always reliable as our own body temperature can affect what we feel, so the best thing to do is invest in a small thermometer with a suction cup- they’re usually less than $2 and can be found at most stores. This will let you know the exact temperature of your tank so you can take any steps needed to keep your fish safe and healthy.


What temperature are heaters preset to?

Most aquarium heaters are preset to a temperature of 25 degrees Celsius (78 degrees Fahrenheit), which is suitable for an average tropical aquarium. Many tropical fish can thrive at this temperature, so many people do not need to adjust the preset temperature. However, adjustable heaters can be turned up or down within a range of 20-30 degrees Celsius (68-86 degrees Fahrenheit) to accommodate different species’ temperature preferences.

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When do I alter aquarium temperature?

The temperature in an aquarium may need to be altered depending on the specific needs of the fish species. For example, if you have Discus, Cardinal Tetras, Rams, or Zebra Plecs, you may need to raise the temperature to ensure their happiness. On the other hand, some tropical fish may require a lowering of temperature to simulate the breeding season. Goldfish, on the other hand, may require a rise in temperature to trigger breeding.

What size aquarium heater do you need?

The size of the aquarium heater you need depends on the size of your aquarium. It is recommended to have one watt of heater power per liter of aquarium water. For example, a 200-watt heater is suitable for a 200-liter aquarium. It is important to invest in a good quality heater to ensure the survival of your tropical fish. Always use a separate thermometer to accurately measure the water temperature.


In conclusion, finding the ideal temperature for your tropical fish tank is crucial for the health and happiness of your aquatic friends. It may require some trial and error, but with patience and the right equipment, you can create a comfortable and thriving environment for your fish. So, dive in and create a tropical paradise for your beloved aquatic companions!