Betta Tank Mates: What Sources Report as Suitable or Risky

Which fish, shrimp and set-ups are reported as workable or risky with Betta splendens, where water parameters overlap, and the behaviour that shows a pairing is failing.

Betta splendens can share a tank only with small, peaceful, short-finned species that do not nip fins, and at least one specialist reference advises keeping it alone. The main risks are other male bettas, fin-nippers, and colourful long-finned fish. Whether shrimp survive depends on the individual betta, so no pairing is guaranteed.

What the sources say overall

Seriously Fish says the species is not recommended for the standard community aquarium and is best kept alone. It notes that ornamental strains seem more aggressive than any other Betta species and that in most cases only one individual can be kept per tank. Wikipedia takes a less restrictive view. It says bettas get along with many aquarium fish under the right conditions and are aggressive mainly toward fish smaller and slower than themselves, such as guppies. Care guidelines from the Anabantoid Association of Great Britain, issued with fish health specialist Dr Peter Burgess, say a male may live in a community tank with peaceful species that lack long fins. Temperament varies greatly between individual males, which makes any compatibility prediction unreliable.

Fish the sources advise against

Other male bettas: according to the association's guidelines, adult males will fight, often to the death. Males and females are kept apart except for breeding.
Fin-nippers: Seriously Fish says the tiger barb (Puntigrus tetrazona) is notoriously aggressive and known for biting the fins of other fish. It advises against keeping tiger barbs with timid, slow-moving or long-finned species, anabantoids included. Keeping tiger barbs in a group of at least 8–10 reduces nipping but does not remove the conflict with a slow, long-finned betta.
Long-finned or showy fish: male bettas may attack other long-finned fish such as male guppies, and Seriously Fish advises avoiding species with a similar body shape or trailing fins.

Gouramis and other labyrinth fish

Gouramis are anabantoids, as bettas are. The Seriously Fish profile of the dwarf gourami (Trichogaster lalius) warns that adding other anabantoids, bettas included, or gaudy species such as guppies can make some male dwarf gouramis very aggressive. Bettas also react badly to fish that look like rivals, so the sources give no basis for treating a betta and a gourami as a reliable pairing.

Companions reported in sources

Tropical Fish Hobbyist describes a well-planted tank with mild-mannered tankmates such as small tetras or small rasboras. Fishkeeping retail guidance says companions should be small, but not so tiny that they are mistaken for food, and peaceful with no tendency to nip fins. Seriously Fish calls the harlequin rasbora (Trigonostigma heteromorpha) very peaceful and an ideal companion for shy anabantoids such as Sphaerichthys or the smaller Betta species. That statement refers to the smaller wild bettas and does not specifically assess ornamental B. splendens. Harlequins should be kept in groups of at least 8–10.

Temperature and water parameter overlap

Betta splendens: 22–30 °C, pH 6.0–8.0, 1–15 dGH (Seriously Fish). The association's guidelines give 24–28 °C with minimal fluctuation and a thermostatically controlled heater.
Harlequin rasbora: 21–28 °C, pH 5.0–7.5, 1–12 dGH (Seriously Fish). The shared range with the betta guidelines is about 24–28 °C, pH 6.0–7.5.
Dwarf gourami: 22–27 °C, pH 6.0–7.5 (Seriously Fish). The parameters overlap, but the temperament conflict described above remains.
Tiger barb: 20–26 °C, pH 5.0–8.0 (Seriously Fish). It overlaps the betta guidelines only at 24–26 °C, and its fin-nipping rules it out regardless.

Matching parameters are necessary but not enough. Temperament and fin shape decide whether a combination works.

Shrimp and snails

Practical Fishkeeping says that success with shrimp comes down to the individual betta's personality and a good deal of chance. Some bettas ignore shrimp entirely, while others hunt down a whole colony in a matter of days. Baby shrimp are the most exposed, because fish eat anything that fits in their mouths. Dense planting and hiding places improve the odds. The shrimp and fish compatibility guide covers this in more detail. The species-level sources consulted for this guide do not assess snails as betta companions, so this guide makes no snail recommendation.

Tank size and set-up

Seriously Fish gives a minimum base of 45 × 30 cm for this species. Wikipedia states that a betta housed with other fish needs at least 45 litres. The association's 5-litre figure is an absolute minimum for a single betta kept on its own, not for a community. Seriously Fish recommends a well-planted, shady tank with floating plants, driftwood and other shelter, and gentle water movement, such as an air-powered sponge filter, because the species comes from sluggish water. Bettas breathe air at the surface and jump well. For that reason the tank needs a close-fitting cover and an air gap above the water.

Signs of aggression and stress

Flared gill covers, extended fins and intensified colour aimed at a tankmate (Wikipedia).
Fin nipping, either by the betta or directed at it.
Pale horizontal bars on the body, which Wikipedia links to stress or fright.
Flaring at its own reflection. This is normal display behaviour and does not by itself show that a pairing has failed.

General stocking principles are covered in the fish compatibility guide, and handling hostility between fish is covered in the managing aggression guide.