Betta fish tank mates depend on the tank more than on the betta. In a small tank of around 5 gallons, the honest answer is very few, and often none. Never add another betta. Veterinary sources name snails and shrimp as possible companions, but fish need more room: RSPCA Australia advises at least 40 liters (roughly 10.5 US gallons) for one betta plus a shoal of small fish. A betta kept alone in a good tank is not missing out. If you add anything, add one kind of animal, slowly, with a backup plan.
That is the short version. The rest of this page explains why, because if I cannot tell you why, I do not think you should do it.
Does a Betta Actually Need Company?
The question usually starts with a feeling: the tank looks empty, and he looks lonely. That is a very human reading of a fish.
None of the veterinary guidance I read says a betta needs a companion. What it does say, firmly, is what happens when the wrong companion is chosen. Dr. Krista Keller, a board-certified specialist in zoological medicine at the University of Illinois, writes in the college's column Your Betta Needs More Than a Bowl (published April 15, 2019, read September 25, 2026) that bettas "are naturally territorial and should not be housed with any other betta fish because they will fight and injure each other, often resulting in death."
So the useful question is not "is he lonely?" It is "would a tank mate make his life better, or just busier?" In a small tank, busier is the more likely result. Every animal you add also adds waste, takes space, and gives him something to defend his territory against.
Rule One: Never Another Betta
This is the one point where every source agrees. Two male bettas in one tank will fight. The University of Florida IFAS fact sheet FA212, Evolution, Culture, and Care for Betta splendens, describes males displaying aggression "almost immediately" on meeting another male, spreading their fins and flaring their gill covers. Breeders separate young males into individual containers once they can be told apart, specifically to avoid damage from that aggression.
RSPCA Australia puts it just as plainly: two males "should never be placed in the same tank."
Female groups, often called sororities, are a different subject with their own risks, and they are not something to try in a small tank. I cover them separately.
Why Tank Size Decides First
Before you look at any list of betta fish tank mates, look at your tank's volume. Here is what the sources I read say about space.
| Setup | What the source says | Source |
|---|---|---|
| One betta, ideal | 20 liters or more (about 5.3 US gallons) | RSPCA Australia |
| One betta, absolute minimum | 10 liters (about 2.6 US gallons) | RSPCA Australia |
| One betta, ideal | "a 5-gallon glass or plastic tank or larger" | University of Illinois |
| One betta plus a shoal of small fish | At least 40 liters (about 10.5 US gallons) | RSPCA Australia |
| Each additional shoal, or a large shoal | An extra 20 liters recommended | RSPCA Australia |
The gallon figures are my own conversions from the liters RSPCA gives. The guidance itself comes from the RSPCA Knowledgebase article How should I care for my Siamese fighting fish? (last updated May 1, 2024, read September 25, 2026).
Put those together and the picture for a 5 gallon tank is clear. It meets the recommendation for one betta. It falls well short of what RSPCA advises for a betta and a group of fish. Dr. Keller makes the same point from the other side: when tank mates are added, "the size of the tank and filtration system must increase to keep everyone healthy and clean."
That is why this page is honest about a small tank. The limit is not the betta's temper. It is the water.
What Can Work in a Small Tank
If your tank is around 5 gallons and you still want something else living in it, the options narrow to animals that are small, slow, peaceful and not shaped like a rival. Dr. Keller's column names "snails, ghost shrimp, certain species of fish, and African dwarf frogs" as tank mates that can be added, with the size and filtration caveat above. In a small tank, that realistically leaves invertebrates.
Snails
A single snail is the least disruptive addition to a small betta tank. Snails are slow, armored, and usually ignored once the betta has inspected them. They graze algae and leftover food, though they also produce waste of their own, so a snail is not a free cleaner.
Some bettas do pick at snail antennae. Watch for that in the first days. If you are considering one, read the full care page first, because different snails have very different adult sizes, diets and breeding habits. My page on nerite snails and why they will not take over a tank is a good place to start.
Shrimp
Shrimp are the option people ask about most, and the one I would be most careful with. A betta is a carnivore that eats insects and small invertebrates in the wild, and small shrimp are close to the size of the live foods bettas are fed. Some bettas ignore shrimp. Others treat them as food, especially young shrimp.
If you try shrimp, give them dense plants and hiding places, and go in expecting that some may be eaten. The same predator problem applies to shrimp colonies generally, which I explain in shrimp tank mates that will not eat the babies.
Fish
In a 5 gallon tank, I would not add fish. Based on the RSPCA figure, a shoal of small fish needs roughly twice the volume of a typical small betta tank. Shoaling fish also need to be kept in a group to behave normally, so "just one or two" of a schooling species is not a kindness either.
What to Avoid, Whatever the Tank Size
Some pairings go wrong often enough that they are best ruled out from the start.
- Any other betta. Covered above, and not negotiable.
- Fin nippers. Some small, fast fish nip at fins. A betta's long, heavy fins are an easy target, and he cannot outswim a quick fish.
- Long-finned or brightly flared fish. A fish that looks like a rival can trigger the same flaring and chasing a betta aims at another male.
- Anything that needs a different temperature. Dr. Keller gives a range of 76°F to 81°F for a betta tank. RSPCA Australia gives 24 to 26°C (about 75 to 79°F). A companion has to be comfortable in the betta's water, not the other way round.
- Anything that will outgrow the tank. Check the adult size of any animal before you buy it, not the size it is in the shop.
Betta Fish Tank Mates in a Larger Tank
If you have, or are planning, a tank of 40 liters or more, the options widen. RSPCA Australia lists corydoras, otocinclus catfish and neon tetras (in groups of five or more) as suitable companions in that size of community setup.
I am not recommending a specific species on this page. Before buying any fish, check its adult size, lifespan, temperature range and group size on a proper care source, and check that it is legal to keep where you live. A larger tank gives you more options, but it does not remove the individual temperament of your betta.
How to Add a Tank Mate Without Starting a Fight
If you decide to go ahead, the order you do things in matters more than the species you choose.
- Quarantine the newcomer first. A new animal can carry disease into a tank that was healthy. A separate tank is the simplest protection, and I explain why in quarantine, the cheapest insurance in the hobby.
- Test your water before and after. Every new animal adds waste. A tank that was stable with one fish may not be stable with two species.
- Add one kind of animal at a time. If there is a problem, you will know which addition caused it.
- Give the tank hiding places. Plants and decor that break up sight lines let both animals get away from each other.
- Watch closely for the first days. Look for chasing, repeated flaring at the same animal, or nipping.
- Have a backup plan ready. RSPCA Australia recommends a backup tank in case aggression develops. A second tank or a divider is much easier to set up before you need it.
Signs It Is Not Working
A betta flaring once or twice at something new is normal curiosity. What you are watching for is a pattern.
- He chases or flares at the same animal again and again
- Either animal has torn fins or new marks
- The tank mate hides all the time and stops feeding
- Your betta stops eating, hides constantly, or clamps his fins
RSPCA Australia notes that a fish that is "constantly hiding or appearing lethargic and unresponsive" is likely to be stressed or ill and should get appropriate veterinary care. If separating the animals does not settle things, or if either one shows wounds or signs of illness, contact an aquatic veterinarian. I will not try to diagnose a fish from a description, and a vet who can see him will know far more than any page.
Separating a pair that is not working is not a failure. It is the whole reason to have the backup plan.
Frequently Asked Questions
What are the best betta fish tank mates for a 5 gallon tank?
In a tank of around 5 gallons, the realistic options are invertebrates, such as a single snail or, with some risk, shrimp. RSPCA Australia advises at least 40 liters for a betta plus a shoal of small fish, which is roughly twice the size of a 5 gallon tank.
Can two male bettas live together?
No. The University of Illinois College of Veterinary Medicine states that bettas should not be housed with any other betta because they will fight and injure each other, often resulting in death. RSPCA Australia says the same about two males.
Is my betta lonely on his own?
None of the veterinary sources I read say a betta needs a companion. A single betta in a properly sized, heated and filtered tank is a complete setup. Adding a tank mate is a choice, not a welfare requirement.
Will my betta eat shrimp?
He might. Bettas are carnivores, and small shrimp, especially young ones, are close to the size of the live foods bettas are fed. Some bettas leave shrimp alone and others hunt them, so plan for hiding places and possible losses.
What should I do if my betta attacks his tank mate?
Separate them. That is why a backup tank or divider should be ready before you add anything. If either animal is injured or stops eating afterward, contact an aquatic veterinarian.