A 5 gallon tank has less floor than specialist guidance calls large enough for one betta alone. That guidance is a 45 × 30 cm base, or 1,350 cm². The common 5 gallon tank measures 16 × 8 in, which is 826-875 cm². A school of 8 ember tetras asks for the same 1,350 cm² before the betta arrives.
No published study has put a betta with nano fish or shrimp and counted the losses. Research covers fights between males, tank size and a few 1970s trials with other labyrinth fish. The rest is husbandry advice and keeper reports, and the advice leans one way. Most of it calls the betta best kept alone. RSPCA Australia lists snails and large shrimp as possible companions and asks 40 L for one betta plus one shoal.
Verdicts never transfer between sizes, so every tank mate is rated twice. Five gallons holds a betta alone, snails and perhaps Amano shrimp, with no fish. Ten gallons holds one small group at most.
Betta tank mates for 5 and 10 gallon tanks
- Recommended with precautions
- Conditional depends on the betta
- Unsuitable poor fit
- Not recommended avoid
| Tank mate | 5 gallon | 10 gallon | What decides it |
|---|---|---|---|
No tank mateBetta alone, planted | Recommended | Recommended | Specialist profiles call the betta best kept alone. Five gallons is the usual starting size for one. |
Nerite snailVittina natalensis and kin | Conditional | Conditional | Eggs do not hatch in fresh water, so no colony forms. Needs a tight lid and hard water. A betta may nip the tentacles. |
Malaysian trumpet snailMelanoides tuberculata | Conditional | Conditional | Nocturnal and burrowing, so it avoids the betta. Breeds with every meal, so feed lightly. |
Mystery snailPomacea diffusa | Unsuitable | Conditional | The snail is messy, so 10 gallons is the advised minimum for one. Bettas nip the long antennae, which resemble worms. |
Amano shrimpCaridina multidentata | Conditional | Conditional | Usually left alone, though bettas nip the antennae. Larvae need brackish water, so no shrimplets appear. Keep 1-3 in 5 gallons, 3-5 in 10. |
Red cherry shrimpNeocaridina davidi | Conditional | Conditional | Adults are often ignored, but shrimplets at 1-2 mm are not, and a 5 gallon rarely keeps a colony. In 10 gallons, start with 10 in dense moss. |
Ghost shrimpPalaemon paludosus | Not recommended | Conditional | Sold as feeders. Some are Macrobrachium prawns that attack bettas. Orange bands on the antennae and claws mark a true Palaemon. |
Crystal and bee shrimpCaridina cantonensis group | Not recommended | Not recommended | Need 62-76 °F water and KH 0-4. A betta tank at 77-80 °F misses the range. |
Ember tetraHyphessobrycon amandae | Not recommended | Conditional | The best-supported fish. Groups of 8-10 need a 45 × 30 cm base. Three keeper reports describe a betta killing embers in 9, 10 and 12 gallons. |
Pygmy corydorasGastrodermus pygmaeus | Not recommended | Conditional | Swims in midwater, not on the bottom, and is easily intimidated. Needs a group of 6-10. The betta can steal sinking food. |
Lambchop and harlequin rasborasTrigonostigma spp. | Not recommended | Conditional | Groups of 8-10 want a 60 × 30 cm base, and a 10 gallon covers 72-76% of it. The 30 mm lambchop fits better than the 45 mm harlequin. |
Chili rasboraBoraras brigittae | Not recommended | Conditional | Timid, and keepers report chilis hiding for good beside a betta. Skip B. merah and B. maculatus, which need soft, acidic water. |
Neon tetraParacheirodon innesi | Not recommended | Unsuitable | Even neons nibble long fins, in keeper reports and magazine advice. Needs a 60 × 30 cm base, and the range tops out at 25 °C. |
Celestial pearl danioDanio margaritatus | Not recommended | Unsuitable | Needs 20 or more fish, 20-26 °C and no driftwood. A warm, planted betta tank works against all three. |
Kuhli loachPangio semicincta | Not recommended | Unsuitable | Needs a 60 × 30 cm base for 5-6 fish. Escapes through any gap in the lid. |
Guppy and Endler’s livebearerPoecilia spp. | Not recommended | Not recommended | The Anabantoid Association names the male guppy as a fish bettas attack. Both want hard water, up to 35 dGH for Endler’s livebearers. |
Tiger barb, serpae, zebra danioFin nippers and fast swimmers | Not recommended | Not recommended | A poor companion for long-finned and anabantoid fish. Bases run 80 × 30 to 90 × 30 cm. |
Gouramis and other bettasRival labyrinth fish | Not recommended | Not recommended | Bettas can turn some male dwarf gouramis very aggressive. Two male bettas fight to the death. |
Ratings assume a heated, filtered, planted tank and a spare tank on standby.
Floor space decides more than gallons
Gallons measure depth as much as area, and schooling fish need length. Species profiles state tank sizes as base dimensions for that reason.
| Tank or base | Floor | Share of betta-alone base | Scale |
|---|---|---|---|
5 gallon (Tetra)16 × 8 in | 826 cm² | 61% | |
5.5 gallon (Aqueon)16 3/16 × 8 3/8 in | 875 cm² | 65% | |
10 gallon (Tetra)20 × 10 in | 1,290 cm² | 96% | |
10 gallon (Aqueon)20 1/4 × 10 1/2 in | 1,372 cm² | 102% | |
One betta, or 8-10 embers or chilis45 × 30 cm · species-profile base | 1,350 cm² | 100% | |
8-10 neons, harlequins or kubotais60 × 30 cm · species-profile base | 1,800 cm² | 133% |
The dark line marks 1,350 cm². Aqueon and Tetra list overall dimensions, so interior floors are slightly smaller.
A betta alone uses the same 1,350 cm² as a school of embers. No profile says the figures add up, and no source gives a combining rule. A 10 gallon covers the base of one species. In a 10 gallon, neon, harlequin and kubotai schools fall 24-28% short of their base before a betta arrives.
RSPCA Australia asks about 40 L for a betta and one shoal, or 10.6 gallons. A 10 gallon holds 37.9 L by label and less with substrate and a gap below the rim. Some lists that stock 5 gallons with 13 to 15 species give groups of 2 or 3. Species profiles advise 8-10 for those fish and 20 or more for celestial pearl danios. Neons and white clouds showed less aggression in larger groups (Saxby 2010). Tiger barbs ate less alone or in pairs than in fours (King and Volkoff 2025).
Five gallons: the betta alone, then snails
Plants, a lid and a heater make a complete 5 gallon tank. A 25 W heater suffices in a covered tank in a room at 68 °F or above. Aqueon rates a 50 W heater for 5 to 20 gallons, which suits a colder room. One or two nerite snails add algae control with no breeding. Amano shrimp come next, then cherry shrimp as an experiment.
No fish holds up. One keeper reports 8 embers healthy beside a betta in 5 gallons. A 5 gallon floor is 65% of the base advised for embers alone, and three reports end in dead embers at 9 to 12 gallons. Community-tank advice starts at 10 to 20 gallons. Small water masses also swing faster in temperature and chemistry, which shrimp tolerate worst. More fish for this size are in the 5 gallon fish guide.
Ten gallons: one group, never two
Ember tetras are the best-supported pick. Advice runs from 10 gallons with 5 or 6 fish to 15 gallons for 9 to 10, and the species profile asks 8-10 on a 45 × 30 cm base. Choose 8 to 10 and add the school first, an order keepers favor and no study tests.
Pygmy corydoras come second. The profile advises 6 to 10 or more on the same base and places them in midwater, where the betta patrols. Lambchop and chili rasboras follow on weaker evidence. A second group is too much, since RSPCA Australia adds 20 L per extra shoal. A true community starts near 20 gallons, covered in the 20 gallon fish guide.
Shrimp with a betta
Keepers and shrimp sellers report that bettas split three ways. Some pick off the occasional fry, some ignore shrimp, and some cause carnage. Nothing reveals beforehand which kind a given fish is. Adult cherry shrimp reach 3-4 cm. Hatchlings are 1-2 mm miniature adults, which makes them the usual victims. Amano shrimp avoid the problem, since their larvae need brackish water.
No source counts how many shrimplets survive. Dense moss, leaf litter and tangled stems give cover. A lab study of insect and fish predators found plant shape mattered while density did not (Warfe and Barmuta 2004). Sellers advise adding shrimp before the betta. No lab data supports the claim that 78-80 °F (25.6-26.7 °C) harms cherry shrimp. Survival stayed high at 24, 28 and 32 °C, culture was best at 28 °C, and egg loss began at 32 °C (Tropea 2015).
Copper and pesticides matter more than cover. Copper in fish medicine kills shrimp and snails, so treat a sick betta in a separate tank. Pesticides on new plants have killed shrimp, and shrimp breeders advise watering new plants for several weeks before planting. Drip-acclimate shrimp over 1.5 to 2.5 hours with the lights off. The shrimp-safe fish guide rates more species.
Why one betta ignores shrimp and the next hunts them
Individual variation is measured and repeatable. Ornamental males tested weekly differed widely in aggression, and some showed none (da Silva 2025). Fighting-bred strains are more aggressive than wild fish in fight-like tests (Verbeek 2007), and females of a fighting line are too (Ramos and Gonçalves 2019). RSPCA Australia calls females often more peaceful but capable of aggression.
Fin type is untested. Both strain studies used short-finned lines, and the claim that veiltails are calmer rests on one retailer. Shop males live alone from 3 to 4 months of age (UF/IFAS), and whether that predicts behavior toward tank mates is unknown. A 1970s trial with labyrinth fish found that less space raised aggression toward other species too. The only reliable test is the tank itself, so keep a spare tank ready.
How to add tank mates
- Cycle the tank without fish until ammonia and nitrite read 0 on a liquid test.
- Plant heavily first. Floating plants, moss and tall stems break sight lines, and RSPCA Australia advises extra cover.
- Quarantine new fish for 2 to 6 weeks, since sources disagree on the length.
- Drip-acclimate shrimp. Float fish bags, then add tank water in steps over 30-60 minutes.
- Add the school or shrimp first and the betta last. For a resident betta, use a clear divider or a holding tank for several days. No study compares the orders.
- Do not rely on rearranging decor. Fish magazines say it resets territories in territorial fish, but no betta source tests it.
- Watch for 72 hours. Flaring at tank mates, chasing, torn fins and a hiding school mean trouble.
- Separate at the first sustained chasing, torn fin or death. A betta study separated pairs after three consecutive bites (Oldfield and Murphy 2024).
- Add the next animal only after 2-3 weeks of stable nitrate readings.
Fish that fail, and the exact reason
Fin nippers fail first. Tiger barbs, serpae and black skirts bite long fins, and RSPCA Australia names widow, serpae and cochu’s blue tetras. Male guppies and Endler’s livebearers read as rival males. Clown loaches and pea puffers nip, and the clown loach profile names bettas as its victims.
Water rules out the next group. White clouds need 14-22 °C, goldfish need cooler water, and mollies, platies and Endler’s livebearers need hard, alkaline water. The rest fail on group size. Neons, harlequins, kuhlis and cherry barbs need numbers that a 10 gallon floor cannot hold beside a betta.
Water that suits a betta and its tank mates
Hold 24-26 °C, the overlap of RSPCA Australia’s betta range with embers, pygmy corydoras, cherry shrimp and Amano. The shared chemistry is pH 6.5-7.0 and 6-8 dGH. A betta tolerates ammonia far better than most fish (Kajimura 2023), so a calm betta proves nothing about the water. Test with a liquid kit.
Bettas need gentle flow. Species guidance suggests 80-125 L per hour for a betta tank. The pump in one common 5 gallon kit turns 19 L over 11 to 16 times an hour. Choose an air-driven sponge filter, which also keeps shrimplets out of the intake, and a thermostat-controlled heater.
Sources
- RSPCA Australia, Siamese fighting fish care (2024)
- Watson et al. 2019, Betta splendens culture and care, UF/IFAS
- Oldfield and Murphy 2024, Animal Welfare
- Verbeek et al. 2007, Animal Behaviour
- Ramos and Gonçalves 2019, Frontiers in Zoology
- da Silva et al. 2025, Acta Ethologica
- Tropea et al. 2015, PLOS ONE
- Warfe and Barmuta 2004, Oecologia
- Kajimura et al. 2023, BMC Zoology
- Saxby et al. 2010, Applied Animal Behaviour Science
- King and Volkoff 2025, tiger barb group size
- Aqueon critical dimensions
