What Water Temperature Do Betta Fish Need? Ideal Range
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What temperature of water do betta fish need? The two care guides used for this article give slightly different ranges: PetSmart’s guide says 77 to 82 degrees Fahrenheit (23 to 27 degrees Celsius), and Chewy’s guide says 76 to 81 degrees, ideally toward the upper end. In practice that points to the high 70s to low 80s Fahrenheit, held steady with a heater and checked with a thermometer. This page walks through the numbers, how the two sources differ and what to do about it.
Quick answer
- Aim for the overlap of the two guides: about 77 to 81 degrees Fahrenheit.
- Both guides call for a heater, and both pair it with a thermometer.
- Chewy’s rule of thumb is about 1 watt per liter of water; PetSmart’s is 5 watts for each gallon.
- If your betta looks unwell or the tank swings in temperature, ask a vet; this article gives no treatment advice.
The range the sources give
PetSmart’s care guide states the water should be kept around 77 to 82 degrees Fahrenheit (23 to 27 degrees Celsius). Chewy’s guide gives 76 to 81 degrees Fahrenheit as the ideal range, suggests staying toward the upper end, and in its FAQ says bettas thrive in water between 75 and 80 degrees. Put side by side, the sources disagree by a degree or two at each end, not by much. A target in the high 70s to around 80 satisfies both, and the best use of the numbers is to pick a set point in that zone and let the heater hold it.
| Source | Range stated | Heater guidance |
|---|---|---|
| PetSmart betta care guide | 77 to 82 F (23 to 27 C) | 5 watts per gallon; use with a thermometer |
| Chewy betta care guide | 76 to 81 F, upper end suggested; FAQ says 75 to 80 F | about 1 watt per liter; 20 watts at least for 5 gallons |
Why a heater is part of the answer
Chewy’s guide says bettas need a heater to keep the water in range and that the heater should be strong enough to warm the whole tank. PetSmart’s guide lists a filter and a heater among the basics and says you can use an aquarium heater and a thermometer. Neither guide gives a house temperature that is good enough on its own, so the practical reading is simple: a tank that is not heated depends on your room, and rooms change.
For a closer look at that question, see our article on whether betta fish need a heater, and our companion piece on what temperature betta fish like.
Sizing a heater from the sources
The two rules of thumb give different numbers for the same tank. Chewy’s guide says about 1 watt per liter and gives an example: a 5 gallon tank needs a heater of at least 20 watts. PetSmart’s guide recommends 5 watts for each gallon, which would be 25 watts for the same 5 gallons. A 5 gallon tank holds roughly 19 liters, so the two approaches land close together at small sizes. If you are between sizes, the reasonable reading of both is to pick the heater that matches or slightly exceeds the tank volume rather than one that is well below it. Always follow the heater maker’s own instructions for the tank size.
- Check that the heater is rated for the volume of your tank.
- Check that the tank holds enough water for the heater to stay submerged as its instructions require.
- Read the heater packaging for placement; the care guides here do not cover placement.
Related reading: how many gallons a betta needs and how big a tank betta fish need.
Using a thermometer
Chewy’s guide says a thermometer is needed to confirm the water is at the target temperature, and it lists checking that the water temperature is in range among the daily care tasks. PetSmart pairs the heater with a thermometer too. The sources do not rank thermometer types, so the safe takeaway is just to have one in the tank and look at it each day. A heater dial or the label on the box tells you what the heater is set to, not what the water actually reads.
Stability and tank size
Chewy’s guide says larger volumes of water are less likely to be affected by fluctuations in water chemistry or temperature. That is the one statement about stability in the two sources. It is a good reason to avoid very small containers, although the two sources disagree on the minimum tank size: PetSmart says at least 3 gallons with a filter and a heater, while Chewy’s article gives 10 gallons in one place and at least 5 gallons in its FAQ. Because the sources disagree, look at our tank size articles linked above and then pick the largest tank you can accommodate.
Water changes and temperature
Chewy’s guide recommends regular water changes: 15 to 25 percent weekly and 25 to 50 percent monthly, with a larger change if nitrate is high or any nitrite is detectable. It says new water should be treated with a conditioner to remove chlorine and heavy metals. The sources do not say what temperature the replacement water should be, so match it to the tank by checking with the thermometer before and after the change instead of guessing. Our article on hard water and betta fish covers the water-quality side.
Adding a new betta
PetSmart’s guide says to float the bag for 15 minutes so the fish can get used to the new water temperature. That is the only acclimation step in the source, so follow the seller’s instructions too.
What the sources do not say
Neither guide describes what happens to a betta in water that is too cold or too hot, and neither gives a safe emergency range. This article does not either. If you suspect your betta is ill, ask a vet who treats fish. Do not rely on a general article for treatment.
FAQ
What is the safest single number to aim for?
Both guides include 77 to 80 degrees Fahrenheit inside their ranges, so a set point in that area satisfies both. Chewy suggests staying toward the upper end of its range.
Do I need a thermometer if I have a heater?
Yes. Chewy’s guide says a thermometer confirms the water is at the target temperature.
How many watts should the heater be?
PetSmart gives 5 watts per gallon; Chewy gives about 1 watt per liter, or at least 20 watts for 5 gallons. Follow the heater maker’s guidance for your tank volume.
Is room temperature enough?
Both guides list a heater among the needs, so neither treats an unheated tank as the standard setup.
Can I use tap water?
Chewy’s guide says tap water is fine with a conditioner or dechlorination drops, and PetSmart says to use dechlorinated water.
Bottom line
Pick a set point around 78 to 80 degrees Fahrenheit, use a heater sized for your tank, check a thermometer every day, and ask a vet if your fish seems unwell.
