What temperature is good for freshwater tropical fish?

So you've started an freshwater tropical fish aquarium. The decor is perfect, the water has been de-chlorinated and you're ready to buy some fish. But, wait! Have you checked the temperature of your aquarium water? If you add new fish and aquatic plants to an aquarium that is too cold, or too warm, you aquarium is less likely to thrive. Regular maintenance of aquarium water, including close attention to water temperature, will ensure that your freshwater tropical fish aquarium stays healthy.


Freshwater tropical aquariums should be kept at approximately 25 degrees C (77 degrees F) for optimal fish health. Although tropical fish can survive in water ranging from 22.2 degrees C to 27.8 degrees C (72 degrees F to 82 degrees F), it is best to hover around the 25 degrees C (77 degrees F) mark.


There are a few ways to keep track of the water temperature in your freshwater aquarium. Floating thermometers roam the tank, giving a constant reading. Adhesive thermometers can be placed on the glass front of the aquarium for easy reading. Submergible thermometers may be suction cupped to the interior glass wall of the fish tank. Make sure the thermometer is not placed in an area that may be affected by sunlight. If the thermometer is warmed by the sun on a daily basis, you won't get accurate water temperature results. Avoid placing an aquarium near a window or door, where drafts may also affect the water temperature.


Keeping your aquarium water warm enough for freshwater tropical fish is not difficult. The use of a special aquarium heater, that is submerged into the water, should do the trick. Heaters are rated on their heat output, and sold according to the size of aquarium they need to heat. When purchasing an aquarium heater, be aware of the size of the aquarium it will be placed in.


Do not place your tropical aquarium in the sun to warm the water. The excessive exposure to sunlight will increase the amount of algae growth in the fish tank. Also, the sun cannot be regulated, and the water may get too warm, too quickly, and kill the fish or plants inside.


Tropical fish aquariums that have water at the proper temperature will have clear water and be less likely to grow algae. The water shouldn't feel hot to the touch or have ice on top.The fish and plants should be thriving and moving about normally.

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About the Author

Angela Tague writes marketing content and journalistic pieces for major brands including Bounty, The Nest, Lowe's Home Improvement and Hidden Valley. She also provides feature content to newspapers and writes health and beauty blogs for Daily Glow, Everyday Health and Walgreens. Tague graduated from the University of Iowa with a bachelor's degree in journalism and mass communications in 1999.