So you bought a small betta tank and now you want a bigger one for him

You're in good company

Lots of people start with a tiny "betta bowl" or 2–3 gallon kit, then realise their betta would be happier in 5–10 gallons (or more). Upgrading is the right call. Bettas do better with more space, stable water parameters, and room to swim. The trick is moving him without turning the new tank into an ammonia spike disaster.

Same idea as any tank upgrade

Your small tank's filter is already cycled. Either move that filter to the new, bigger tank and run it there (easiest), or run the new tank's filter on the small tank for 2–4 weeks to seed it, then set up the big tank and move the seeded filter and the betta. Never put a betta (or any fish) into a bigger tank that has a brand-new, uncycled filter — you'll get an instant cycle crash. See our full upgrading your tank guide for step-by-step.

Betta-specific tips

Bettas can be jumpers — keep a lid or leave the water level an inch or two down until you're sure he's settled. He may hide for a day or two in the new space; that's normal. If you add tank mates later, check betta tank mates and stocking for your tank size. Track your tests in App-aquatic so you can see when the new setup is stable.

Quick takeaways

• Use the old filter on the new tank, or seed the new filter in the old tank first.
• Don't put your betta in a bigger tank with an uncycled filter.
• Lid or lower water level to avoid jumps; give him a few days to settle.