Yes. OATA, RSPCA Australia and a University of Illinois vet all call for a heater and a filter in a betta’s tank, and RSPCA Australia and the Illinois vet ask for gentle flow.
Set the water to the temperature your fish need. Aqueon bases its chart on a room at 68 to 72 °F.
Heater size
Each maker’s chart
Aqueon:needs a tank size
Marineland:needs a tank size
Tetra:needs a tank size
hygger:needs a tank size
EHEIM:needs a tank size
Hydor:needs a tank size
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Why a heater
Bettas are tropical fish. The Illinois vet says most homes are kept cooler than a betta needs, so an in-tank heater is needed, and OATA says a heater is required all year.
Water temperature for a betta, by source
Source
Range
In the other unit
RSPCA Australia
24–26 °C
75.2–78.8 °F
OATA
20–28 °C
68–82.4 °F
University of Illinois vet
76–81 °F
24.4–27.2 °C
76 to 78.8 °F (24.4 to 26 °C) is inside all three ranges.
RSPCA says every heater must be controlled by a thermostat, and since heaters and thermostats can fail, to check the water with a digital thermometer every day.
Why a filter, and how gentle
OATA says a filter is always essential, whatever the tank size. RSPCA Australia asks for a filter of the right size with adjustable flow, because bettas prefer low flow, and the Illinois vet says a low-flow filter is vital so the suction can’t injure their fins.
Aqueon’s filter guide gives four to six times the tank’s volume an hour for most tanks, and in the same article says bettas need a gentler flow than a fish like a danio. See what size aquarium filter.
Heater safety
Unplug the heater before your hands go in the water, and never run it out of the water (Aqueon). Let it cool in the water before you lift it out: Marineland says at least 15 minutes, EHEIM 30.
Common questions
Can a betta live without a filter?
No. OATA says a filter is always essential whatever the tank size, and RSPCA says no fish should be kept without a well set up and maintained filter.
Is room temperature warm enough for a betta?
No, says RSPCA Australia: normal room temperature is generally too cold for a Siamese fighting fish, and it can fluctuate.
Care comes from OATA, RSPCA, RSPCA Australia and a University of Illinois veterinary column, heater sizes and safety from Aqueon’s, Marineland’s, Tetra’s, hygger’s, EHEIM’s and Hydor’s charts and manuals, and filter flow from Aqueon. Checked against published data from Aqueon, Marineland, EHEIM, Hydor and Tetra (plus 5 more).
See all 14 sources
Aqueon, Fully Submersible Aquarium Heater instruction manual (Pro heaters, August 2020): Heater Guidelines, Appliance Specification and safety instructions
EHEIM, thermocontrol aquarium heaters 25 to 300 (product pages)
EHEIM, thermocontrol operating manual (3611 to 3619)
Hydor, THEO submersible heater (product page)
Hydor, ETH external (in-line) heater (product page)
hygger, ETL Certification Aquarium Heater (hygger's own store, product page)
RSPCA, Ornamental fish: Environment (“Choosing an aquarium”)
OATA (Ornamental Aquatic Trade Association), How to care for bettas, September 2022 (PDF)
RSPCA Australia knowledgebase, How should I care for my Siamese fighting fish?
University of Illinois College of Veterinary Medicine, “Bettas Need More Than Bowls” (pet health column, 2019)
Aqueon, “How to Choose the Best Filter for You and Your Tank” (maker article)
General care guidance from animal welfare charities, vets and makers' published sizes. It isn't veterinary advice: if your pet seems unwell or has eaten something it shouldn't, call your vet.