Betta: tank size, group & compatibility data

Stocking notes

A territorial labyrinth fish; individual temperament varies and tankmate choices require caution.

For planning, StockingLab models Betta at its approximate adult size rather than the juvenile size commonly seen in shops. That matters because space use and waste production can change dramatically as fish mature.

What the calculator checks

• Whether the tank's usable volume is below the 25 L / 6.6 US gal reference minimum.
• Whether the selected group is below the planner's typical 1 fish social starting point.
• Whether target temperature and pH sit inside the planning range.
• Whether prospective tankmates create predation, fin-nipping, territorial or water-overlap conflicts.
• Whether too many fish accumulate in the same top swim zone.

Before buying

Use this profile as a shortlist tool, not as a substitute for a dedicated care source. Confirm adult size, diet, sex ratio, habitat structure and locally relevant water conditions before purchase.

How to interpret this Betta profile

At roughly 6.5 cm / 2.6 in adult length, Betta should be planned at mature size rather than the smaller size commonly offered for sale. The reference tank is 25+ L / 6.6+ US gal, with a planning water window of 24–28°C and pH 6–7.8. A midpoint around 26.0°C and pH 6.9 is useful only as a comparison aid; the aim is stable water that overlaps the needs of the whole community.

The profile does not assume a school. Individual temperament, territory and the rest of the community therefore matter more than simply increasing numbers. The modeled waste factor is 0.90×, so biological load is only one part of the decision; adult space, group size and swim-zone crowding still need to be checked. Activity is modeled at 0.65×, but lower activity should not be mistaken for permission to compress the fish into an undersized footprint.

Common planning mistakes to avoid

• Check prospective tankmates for fin-nipping behavior and persistent chasing.
• Provide visual breaks and enough territory so one fish cannot control the whole footprint.
• Check that the planned temperature sits inside the shared 24–28°C range for every species in the community.
• Use the 25 L / 6.6 US gal reference as a starting point, then let actual tank dimensions, filtration and the full stock list refine the decision.

Bottom line: the profile is designed to screen a proposed aquarium for obvious pressure points. A result that passes StockingLab still needs to be checked against current, species-specific husbandry information for Betta splendens, especially diet, breeding behavior, sex ratio and habitat structure.