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Chapter 3Tanks and setupsSetup

Betta Fish Tank Setup: Tank Size, Heater, Filter and Decor

How to set up a betta tank: 5 gallons or more, a heater for 76 to 81°F, a gentle filter, a lid and soft decor, from University of Illinois vets and the RSPCA.

By Fish Supplies editorial teamUpdated 4 min readHow we research

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A dark blue-green betta swimming among green plants in a home aquarium

A betta needs a tank of 5 gallons or more with a lid, a heater holding 76 to 81°F, a low-flow filter and soft decor, say University of Illinois vets. RSPCA Australia agrees on the size (20 liters or more) and adds weekly 10 to 25 percent water changes. Bettas live alone: two will fight.

How big should a betta tank be?

The sources line up closely on size:

Source Tank size Notes
University of Illinois vets 5 gallons or larger Never a bowl: bowls are too small for normal swimming and hiding
RSPCA Australia 20 liters or more ideal, 10 liters the absolute minimum 20 liters is about 5.3 gallons
Aqueon (maker) Standard 5.5 gallon tank: 16.2 x 8.4 x 10.5 in, 62 lb full A common betta tank size

Illinois vets say a larger tank lets the fish behave normally and slows the build-up of toxins. A standard 5.5 gallon tank meets both sources. See tank sizes compared for the next sizes up.

Betta tanks and kits from 5 gallons

Shop betta tanks, 5 gallons and up

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A lid, with an air gap

RSPCA Australia calls bettas excellent jumpers and says the tank needs a lid. Bettas also take occasional breaths of air from the surface, so leave a small gap between the water and the lid. If you buy a kit, check that a lid is in the box.

Heater and thermometer

Bettas are tropical fish. Illinois vets give 76 to 81°F and say an in-tank heater is needed because most homes are kept cooler. RSPCA Australia gives a slightly narrower 24 to 26°C (75 to 79°F) and says room temperature is too cold and fluctuates too much.

For a 5 or 10 gallon tank, Aqueon’s heater wattage guidelines list a 50 watt heater (rated for 5 to 20 gallons). An adjustable heater lets you set the exact temperature; check it with a separate thermometer. The aquarium heaters chapter covers sizes and safety, including Aqueon’s advice to unplug a heater and let it cool for 30 minutes before taking it out of the water.

Small adjustable heaters for 5 to 10 gallon tanks

Shop aquarium heaters, adjustable and preset

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A gentle filter

Bettas have long, delicate fins. Illinois vets call for a low-flow filter so the fish’s fins are not hurt by the suction, and RSPCA Australia asks for efficient filtration with an adjustable flow, since bettas come from slow water. Sponge filters and small filters with a flow control both fit. The filters chapter compares the types.

Treat tap water with a dechlorinator, as Illinois vets advise; they add that distilled water lacks the minerals fish need. Then cycle the tank before the betta arrives, as in how to cycle a fish tank.

Plants, hammocks and decor that spare the fins

RSPCA Australia says bettas come from densely planted water and prefer a tank with several plants, real or artificial, over smooth gravel with no sharp edges. Illinois vets add that decorations should never fill so much of the tank that the fish is pushed to the edges.

  • Silk plants are soft on fins. Hard plastic plants can have sharp edges: run a finger along them first.
  • Leaf hammocks are small artificial leaves on a suction cup, placed near the surface as a resting spot.
  • Live plants are sold by aquarium retailers; we do not link them. Check the retailer’s care notes for your light.

More on gravel, sand and decor is in substrate and decor.

A small rimless planted aquarium with a hang-on filter and a clip-on light
A small planted tank with a hang-on filter. For a betta, pick a filter with an adjustable flow.

Only one betta per tank

VCA’s aquarium guide says one male betta per tank. Illinois vets go further: bettas are territorial and should not share a tank with any other betta, because they fight and injure each other, often fatally. RSPCA Australia says two males should never be placed in the same tank.

Feeding and water changes

Feeding advice differs by source. RSPCA Australia says once a day, only what the fish eats in under two minutes. Illinois vets say daily, the amount eaten in 3 to 5 minutes, with treats such as freeze-dried bloodworms in moderation. Hikari’s Betta Bio-Gold label says 5 to 10 pellets up to three times a day, depending on the betta’s size. All agree on one point: remove what is not eaten. See fish food by fish.

For water, RSPCA Australia suggests weekly partial changes of 10 to 25 percent with a gravel clean. The cleaning chapter compares that with other sources’ schedules. If your betta looks unwell, see a veterinarian who treats fish.

The setup checklist lists everything else a new tank needs, and gifts for aquarium keepers has ideas for the betta keeper in your life.

Frequently asked questions

Is a 5 gallon tank enough for a betta?

Yes, by the veterinary advice: University of Illinois vets say a betta should ideally be in a 5 gallon tank or larger. RSPCA Australia's ideal of 20 liters or more is about 5.3 gallons, so the two sources agree closely.

Do bettas need a heater?

Yes. Illinois vets say bettas are tropical fish that need 76 to 81°F, and that most homes are kept cooler, so an in-tank heater is needed. RSPCA Australia says room temperature is too cold and fluctuates.

Do male bettas get lonely?

The sources do not describe loneliness; they describe fighting. Illinois vets say bettas should not be housed with any other betta because they fight and injure each other, often to the death, and VCA says one male per tank.

How many bettas can be in a 5 gallon tank?

One. Both University of Illinois vets and RSPCA Australia say two bettas will fight, and VCA lists bettas as one male per tank.

Does a betta tank need a filter?

Yes, a gentle one. Illinois vets call for a low-flow filter so the suction does not injure the fins, and RSPCA Australia asks for efficient filtration with adjustable flow.

Part of Tanks and setupsStart here: Fish Tank Supplies Checklist: Everything a New Aquarium Needs

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