Nano Fish Compatibility Chart — Who Can Live Together

Compatibility is the question I get more than any other in my inbox. Someone buys a 10 gallon, picks six fish they like at the store, and asks if they can all go in together. Usually the answer is no — not because the fish are delicate, but because the keeper did not think about temperature overlap, water chemistry overlap, or temperament before they bought. This chart is the printable answer. The 20 species below cover 95% of the fish you will see in a nano tank section at any pet store, and the matrix tells you which combinations work, which need conditions, and which will end in tears.

The Three Compatibility Rules

Before you read the matrix, understand the three rules it is built on. Every cell in the table is the result of applying these three rules to a pair of species. If you internalise the rules, you can answer compatibility questions for fish that are not even on this chart.

Rule 1: Temperature overlap. Both species must thrive at the same temperature — not merely survive. A White Cloud Mountain Minnow at 26°C is not thriving; it is overheating, with a shortened lifespan and a stressed immune system. A Neon Tetra at 18°C is sluggish and prone to ich. Find the overlap zone where both species are at their best, not just alive. The chart’s × marks for White Clouds pairings with tropical fish are this rule in action.

Rule 2: pH and GH overlap. Both species must thrive at the same water chemistry. A Shell Dweller wants pH 8.0 and GH 12; an Apistogramma wants pH 6.0 and GH 4. There is no pH where both thrive — only pH values where both barely survive. Most tap water in North America sits around pH 7.4 and GH 8, which is fine for livebearers and hardy community fish but borderline for soft-water species and Tanganyikan cichlids. Test your tap. Match the fish to the tap, not the other way around.

Rule 3: Temperament match. A 5 cm pea puffer and a 4 cm Chili Rasbora are the same size, but the puffer will hunt the rasbora within a week. A 6 cm betta and a 5 cm male guppy are the same size, but the betta will shred the guppy’s fins. Body size is not temperament. Read the temperament row for each species in the fish database before you mix species. The matrix’s ! marks for bettas and long-finned fish are this rule.

The Big Compatibility Matrix

Abbreviations: NT Neon Tetra, ET Ember Tetra, CR Chili Rasbora, CPD Celestial Pearl Danio, PC Pygmy Cory, CS Cherry Shrimp, AS Amano Shrimp, BE Betta, AP Apistogramma, RA Ram, SD Shell Dweller, KR Kribensis, PP Pea Puffer, GU Guppy, PL Platy, SW Swordtail, OT Otocinclus, BP Bristlenose Pleco, WC White Cloud Mountain Minnow, KL Kuhli Loach. Print this page (Ctrl+P) for a paper copy for your fishroom.

✓ Compatible! Compatible with conditions× NOT compatible— Same species (see notes)

Can Bettas Live with Tetras?

Short answer: it depends on the betta and on the tetra. The matrix shows ! for Neon Tetra and ✓ for Ember Tetra — the difference is body shape and fin length. Ember tetras are short-finned, peaceful, and stay under 2 cm — they do not trigger the betta’s "long-finned rival" instinct. Neon tetras are similar but slightly larger and faster, and some bettas view them as a threat. Serpae tetras, black skirt tetras, and any tetra known for fin-nipping is an automatic × — the tetras will shred the betta’s fins within days.

The bigger variable is the betta. Half the bettas in the hobby ignore everything in the tank. The other half attack anything with colour or movement. You do not know which you have until you put him in a community tank. If you want to try the pairing, set up a 10 or 20 gallon heavily planted, add the tetras first, let them settle for a week, then add the betta last. Have a backup tank or a hospital cup ready. If the betta attacks tetras within 48 hours, pull the betta — he is a solo fish.

The other failure mode is the betta being picked on. Fast, nippy tetras can stress a betta to death without ever touching him. The betta stops eating, hides in the corner, and fades over two weeks. If you see this pattern, pull the betta — he is being bullied even if no fins are missing. Bettas do best alone or with very calm, short-finned tankmates in a heavily planted tank where they can claim a territory. Most "community betta" attempts fail; the successful ones are in 20 gallon+ tanks with Ember Tetras, Chili Rasboras, or Pygmy Corys and a dense plant layout.

Can Shrimp Live with Fish?

The honest answer: most fish will eat shrimp eventually. The question is not whether the fish will hunt the shrimp — they will — but whether the shrimp can outbreed the predation. Cherry shrimp in a heavily planted 20 gallon with a school of Ember Tetras or Neon Tetras will survive, breed, and slowly grow a colony. The tetras eat the babies; the shrimp drop 30 babies a month and 5 survive to adulthood. The colony grows. The same shrimp in a 10 gallon with an Apistogramma or a Betta are gone in 2 weeks.

Amano shrimp are a different story. Adult Amanos are 5–7 cm — large enough that most nano fish leave them alone. Amanos live with tetras, guppies, dwarf cichlids, and even small plecos without being eaten. They are also better algae eaters than Cherry shrimp. The catch is that Amano shrimp do not breed in freshwater — their larvae need brackish water — so what you buy is what you have. No colony growth.

If you want a shrimp-only tank, the answer is simple: do not add fish. A 10 gallon with 20 Cherry shrimp, Java moss, a sponge filter, and nothing with fins is the highest-success shrimp setup in the hobby. Adding even one fish changes the tank from "shrimp tank" to "fish tank with shrimp that are slowly being eaten." The dwarf cichlids (Apistogramma, rams, kribensis), bettas, and pea puffers all get × on the shrimp row because they actively hunt shrimp — not opportunistic predation, but dedicated hunting. They will clear a 20 gallon of Cherry shrimp in a month.

Can I Mix Apistogramma Species?

No. Two Apistogramma species in the same tank will either hybridise or fight, and usually both in that order. The genus Apistogramma has 90+ described species and most of them share the same body plan, the same territory structure, and the same courtship behaviour. A male A. cacatuoides sees a female A. agassizii as a potential mate, not a rival — until they spawn, at which point the hybrid fry are sterile or deformed and you have ruined the bloodline of both species.

The territory problem is the second issue. Every Apistogramma species claims a 30 cm patch of substrate as breeding territory. Two species in a 20 gallon long are competing for the same two-square-foot territory. One pair wins; the other pair is battered into hiding and stops eating. Even in a 40 gallon breeder with sight-line breaks, two Apistogramma species is risky. I have done it; the fish survived but neither pair bred, which defeated the purpose.

The rule: one Apistogramma species per tank, period. If you want a harem (one male, multiple females of the same species), the minimum tank is a 20 gallon long with three caves. If you want two species of dwarf cichlid in the same tank, pick two species that occupy different niches — an Apistogramma (bottom) with a pair of Laetacara dorsigera (mid-water), or a Tanganyika shell dweller (sand) with a Julidochromis (rock). Same-niche dwarf cichlids do not mix.

Can Pea Puffers Live with Anything?

Only with fast, short-finned nano fish in a heavily planted 20 gallon or larger. The matrix shows ✓ for Otocinclus and Bristlenose Plecos (both armoured, both fast, both ignored by puffers) and ! for Chili Rasboras, Ember Tetras, and White Clouds (fast enough to escape but the tank must be 20+ gallons with heavy planting). Everything else — bettas, guppies, swordtails, dwarf cichlids, shrimp — gets × because the puffer will hunt them.

Pea puffers are not community fish. They are small (3 cm) but they have a beak that evolved to crush snail shells, and they use it on anything they can grab. Long-finned fish (guppies, bettas, male swordtails) are shredded within a week. Shrimp are picked off one by one. Slow-moving nano fish like CPDs are hunted into corners. Even fast tetras get nipped fins in a small tank where they cannot escape.

Pea puffers are also aggressive to each other. The "pea puffer community tank" you see on YouTube is almost always a single puffer in a 20 gallon, or a sexed trio (1 male, 2 females) in a 30 gallon. Two males in a tank under 30 gallons will fight to the death. Sexing pea puffers is hard — males have a darker belly and a line through the eye, but juveniles all look female. The safe path is to keep one pea puffer per tank. If you want a group, buy six juveniles, raise them together in a 30 gallon, and rehome the extra males when they mature.

Can I Mix Livebearers (Guppies, Platies, Swordtails)?

Only if you do not care about the offspring. Guppies and swordtails are in the same genus (Poecilia / Xiphophorus — close enough to hybridise) and they will crossbreed. Platies and swordtails are both Xiphophorus and crossbreed readily. The hybrids are usually drab, often deformed, and frequently sterile. After two generations, your mixed livebearer tank is full of mutts that look like nothing in particular.

The water chemistry issue is the second problem. Guppies, platies, and swordtails all want hard, alkaline water (pH 7.5–8.5, GH 10+) — they do fine in most North American tap water. Tetras and rasboras want soft, acidic water (pH 6–7, GH 4–8). Mixing livebearers with tetras means picking a pH that is too high for the tetras or too low for the livebearers. The ! marks in the matrix for livebearer-tetras pairings reflect this — the fish survive but neither thrives.

The clean path is single-species livebearer tanks. A 20 gallon with 12 male guppies (no females — you control the breeding) is a stunning display. A 20 gallon with 6 platies and a bristlenose pleco is bulletproof. If you want a mixed livebearer tank and you accept the hybridisation, keep only females of one species and only males of another — or accept that every drop of fry after month 3 will be a mutt. There is no way to keep mixed-sex guppies and mixed-sex platies together without producing hybrids.

Can Corydoras Species Mix?

Yes — and this is the one place in the chart where mixing species is actively encouraged. Corydoras of different species school together. Pygmy cory (C. pygmaeus), dwarf cory (C. habrosus), and tail-spot cory (C. hastatus) are the three small species and they intermingle freely. Bronze cory (C. aeneus), sterbai cory, and peppered cory (C. paleatus) are the larger species and they also intermingle. The matrix shows ✓ across the entire cory row because corydoras of any species are compatible with corydoras of any other species.

The hybridisation risk between corydoras species is low — most species in the hobby do not crossbreed, and the ones that do (C. aeneus with C. paleatus) are rarely kept together by accident. The bigger concern is group size. Corydoras are schooling fish and a single cory is a stressed cory. The minimum group is 6 of the same species, not 6 mixed. If you want a mixed cory tank, the minimum is 6 of species A plus 6 of species B — 12 fish — in a 20 gallon long. Fewer than 6 of any one species and they will not display natural behaviour.

Pygmy cory are the nano tank default. They max out at 3 cm, they school in the mid-water column (unlike other corys which stay on the bottom), and they are peaceful with everything except shrimp (they will pick at shrimp babies). A school of 8–10 Pygmy cory in a 10 gallon with a betta or a school of Ember Tetras is one of the best nano tank combinations in the hobby. Skip the bronze cory for anything under 20 gallons — they get too big and too boisterous for a 10.

Frequently Asked Questions