Betta Tank Setup: A 5-Gallon Minimum Build, Step by Step

A correct betta tank is 5 US gallons (19 L), filtered with a baffled or air-driven filter, heated to 25 to 27 °C, and cycled before the fish arrives. The cheapest honest build in 2026 costs about $110 new and about $50 used. Cycling takes 3 to 6 weeks if you do it right, which you should, because the alternative is ammonia poisoning your new fish for the first two months of his life (IBC Exhibition Standards, tank requirements). The 2022 laboratory care review for Betta splendens (PMC9334006) confirms 19 L as the minimum for stable water chemistry in single-male housing.

Parts list

• 5-gallon glass aquarium, any brand. The Aqueon 5-gallon kit and the Top Fin 5.5-gallon kit both work. Rectangle preferred. The cube shape is fine if the footprint is at least 12 by 12 inches. Avoid tall, narrow tanks; bettas swim horizontally.

• Sponge filter, Hygger or Hikari brand, rated 5-10 gallons. About $8 to $12.

• Air pump, Tetra Whisper 10 or Hygger Quiet. About $12.

• Airline tubing and check valve, $3 set.

• Preset heater, 25W, Fluval P25 or Eheim Jager 25. About $25. Avoid sub-$10 heaters; they fail stuck-on and cook the fish.

• Thermometer, stick-on or glass. $3.

• Substrate, 2 to 5 lb of inert aquarium sand (CaribSea Super Naturals, Black Diamond Blasting Sand) or fine gravel. About $15.

• Hardscape, one piece of Mopani or spiderwood driftwood, boiled to sink. $10 to $20.

• Plants, 3 to 5 starts of Anubias nana, Java fern, cryptocoryne wendtii, Java moss. $20 total at a fish store, $12 online.

• Glass lid if not included in the kit. $15.

• Water conditioner, Seachem Prime. A 100 ml bottle lasts a year. $8. Seachem Prime on Amazon Affiliate link. See our disclosure.

• Test kit, API Freshwater Master Kit. $30. Buy it, not the strips. API Freshwater Master Test Kit on Amazon Affiliate link. See our disclosure.

Total about $110 new.

Layout

Footprint over height. A 20-long (30 inches × 12 × 12) is a better betta tank than a 20-high (24 × 12 × 16), because the fish uses the floor area and surface area; vertical swimming is a stress response, not exercise. In a 5-gallon, stick with the standard 16 × 8 × 10 inch rectangle.

Substrate 1 inch deep. Deeper sand traps anaerobic pockets and releases hydrogen sulfide when disturbed. One inch is enough to root plants.

Hardscape placed off-center, in the rule-of-thirds spot. Gives the fish sight-line breaks and hiding space.

Plants: tie Java fern and Anubias to the driftwood with cotton thread or superglue gel (the cyanoacrylate is inert once cured, this is standard practice). Never bury Anubias rhizomes; they rot. Cryptocorynes go in the substrate. Java moss gets wedged into crevices.

Fill line 1 inch below the rim. Bettas need surface air. Never fill the tank to the top edge.

Cycling the tank

Do not put the fish in an uncycled tank. This is the single most preventable mistake in the hobby.

A cycled tank has a biofilm of Nitrosomonas and Nitrobacter bacteria living on every surface, converting ammonia → nitrite → nitrate. Ammonia and nitrite are acutely toxic. Nitrate is mostly harmless below 40 ppm.

Fishless cycling protocol:

1. Fill and run the tank with filter and heater on.
2. Dose 99% pure household ammonia (Dr. Tim’s Ammonium Chloride or ACE Hardware Janitorial Strength Ammonia, no surfactants) to 2 ppm.
3. Test ammonia and nitrite every 48 hours.
4. When ammonia drops, redose to 2 ppm. When nitrite starts reading, let it climb and process.
5. The tank is cycled when a 2 ppm ammonia dose drops to zero and nitrite is zero within 24 hours.

Expect 3 to 6 weeks. Seeding with a piece of filter media from an established tank (ask a local fishkeeping club or a trustworthy shop) cuts this to 7 to 10 days.

When cycled, do a 50% water change to drop accumulated nitrate, then add the fish.

Adding the fish

Float the bag in the tank for 15 minutes to equalize temperature. Then drip-acclimate: siphon a small air-line drip from your tank into a container holding the bag water and fish. Fill to double the starting volume over 45 minutes. Net the fish into the tank. Throw away the bag water; don’t pour it in.

Turn off the room light. Leave the tank completely alone for 48 hours. No feeding. First feed at hour 48 is two or three pellets. If the fish eats, you’re clear.

What not to do

Don’t use a Betta Bowl Kit under $20 that promises “no filter needed.” Those kits make the manufacturer’s margin and cost the fish its life.

Don’t use the starter “ammonia detoxifier” chemicals that claim to substitute for cycling. Seachem Prime is not a cycle replacement; it binds ammonia for 24 hours, which buys time, not a solution.

Don’t rinse filter media in tap water. Chlorine kills the bacteria you spent six weeks growing. Rinse in a bucket of water pulled from the tank during a water change.

Don’t add a snail or shrimp “to help.” Add them as companions after the tank is stable, not as bioload boost. Tank mates are a separate decision.

The tank above, once running, is the baseline. Graduate to a 10-gallon planted setup when you have the itch. The 5-gallon floor is a welfare minimum, not an optimization.

Related on this site

• Betta Fish Care: The Evidence-Based Guide
• Best 5-Gallon Betta Tanks in 2026
• Best Live Plants for Betta Tanks in 2026
• Betta Anatomy: What You’re Looking At When You Look at a Betta
• The Betta Vase Myth: Why Peace-Lily Setups Are Animal Cruelty