Betta Tank Mates UK: Best and Safe Compatible Fish by Tank Size

Keeping a betta with tank mates is one of the most confusing topics in fishkeeping.

Search online, and you’ll find endless lists of “20 fish that can live with a betta”, but very little practical guidance about what actually works in real aquariums, especially in typical UK tanks of 20, 30 or 40 litres.

This is why so many betta community setups fail.

Bettas are territorial fish that occupy the top and middle of the tank. They react strongly to movement in their space, and their behaviour changes depending on tank size, layout, planting, and how other species are introduced. Some bettas tolerate tank mates. Others will attack anything that moves.

The difference is not luck. It’s tank setup, litres, compatibility, and introduction method.

This guide is written specifically for UK fishkeepers, using litres instead of vague gallon advice, and focuses on what is realistically safe, based on real UK home aquariums and the experience of UK betta keepers, not just what is theoretically possible in ideal conditions.

Quick Answer (UK Litres):

• In 20 litres, a betta should live alone. Only snails are realistically safe.
• In 30–40 litres, you can add snails and sometimes shrimp, but fish tank mates are usually a bad idea for beginners in typical UK tanks. 
• In 60 litres and above, a carefully planned betta community tank becomes possible with the right species and layout.

The smaller the tank, the higher the risk. Most failures happen when people try to apply “10-gallon community tank” advice to UK tanks of 30–40 litres without the space and layout that those setups actually depend on.

Quick Navigation:

• Betta Tank Mates Decision Guide (UK Litres)
• Rules Before Choosing Betta Tank Mates
• Betta Tank Mates by Tank Size (UK Litres)
• Best Betta Tank Mates (Low Risk / Medium Risk / Avoid)
• Which Fish Can Be Kept With Betta?
• What Is the Best Fish to Pair With a Betta?
• What Animals Can I Put in My Betta Fish Tank?
• Can Betta Fish Be in a Community Tank?
• Male Betta Tank Mates vs Female Betta Tank Mates
• Tank Mates to Avoid With Bettas
• How to Introduce Tank Mates to a Betta Tank
• Troubleshooting Betta Aggression
• Betta Tank Mate Compatibility Table
• Realistic Stocking Examples (UK)
• FAQ
• Conclusion: The Truth About Betta Tank Mates

Betta Tank Mates Decision Guide (UK Litres)

If you want a simple rule that works for most UK homes:

• 20L or less → betta without fish (snails are safe)
• 30–40L → betta + snails; shrimp only in heavily planted tanks
• 60L+ → small schooling fish and bottom dwellers become realistic

If you’re a beginner, choose the lowest-risk option for your tank size and always have a backup plan to separate fish.

Rules Before Choosing Betta Tank Mates

Before you even think about species, you need the right environment.

Most betta tank mate failures are setup problems, not fish problems. Bettas are territorial fish that patrol the top and middle of the tank. If the layout does not allow other species to avoid that territory, aggression becomes inevitable, no matter how “peaceful” the other fish are.

This is why two identical tanks with the same species can have completely different outcomes.

Checklist before adding anything to a betta tank:

• The tank is fully cycled and biologically stable
  Unstable water parameters increase stress and make bettas more reactive to movement and tank mates.
• Heavy planting or hardscape that breaks the line of sight
  Bettas calm down when they cannot constantly see other fish. Visual barriers are more important than tank volume alone.
• Clear separation of swim zones (top, mid, bottom)
  Tank mates must occupy different areas of the tank. Constant overlap leads to territorial conflict.
• Multiple hiding spots at the bottom and mid-water
  Bottom dwellers and shrimp must have places to retreat where the betta cannot follow.
• The betta is already settled and not stressed
  Adding tank mates to a newly introduced or stressed betta almost always triggers aggression.
• A backup plan (spare tank or divider) if it fails
  Not every betta will tolerate tank mates, no matter how perfect the setup is.
• Understanding that each betta has a different temperament
  Some bettas ignore tank mates completely. Others will attack anything that moves. You cannot predict this in advance.

Without these conditions, even “safe” tank mates can turn into a disaster.

Once these rules are in place, tank size becomes the next critical factor, which is where most online advice becomes vague.

Betta Tank Mates by Tank Size (UK Litres)

Most guides stay vague here. In reality, tank size is the single biggest factor that determines whether betta tank mates work or fail.

Bettas are territorial fish that occupy the upper and middle parts of the tank. If there isn’t enough space for other species to avoid that territory, aggression becomes inevitable.

This is why advice based only on “20–40 litres” is often misleading for UK homes. What really matters is how much usable space, planting, and floor area your tank provides.

Betta tank mates in a 20-litre (≈5-gallon)

This is a betta-only nano tank.

Realistic tank mates:

• Nerite snails
• Ramshorn snails
• Mystery snails

Why this works:
Snails do not compete for territory, stay on surfaces, and are ignored by most bettas.

Why shrimp and fish fail here:
In a 20L tank, there is no room for territorial separation. Shrimp are often hunted, and fish are constantly stressed because they cannot escape the betta’s line of sight.

This is the size where most “betta community tank” attempts go wrong.

Betta tank mates in 30 litres

Slightly more forgiving, but still not a true community size.

Realistic options:

• Snails (very safe)
• Amano shrimp or cherry shrimp (situational, requires heavy planting)

Why fish are still a bad idea here:
Even peaceful bottom dwellers do not have enough floor space to avoid the betta’s territory. The tank may look bigger, but behaviourally it functions like a nano tank.

This is where a lot of misleading online advice causes problems for beginners.

Betta tank mates in 40 litres

This is the first size where careful fish choices start to become possible.

Possible with the right layout and planting:

• Snails
• Shrimp
• Very small bottom dwellers, such as pygmy corydoras (with caution)

Important rule at 40L:
You must choose between:

- snails + shrimp or a small group of bottom fish, not both.

Why?
Overstocking reduces floor territory and increases constant interaction, which triggers aggression. Overstocking is the silent killer of betta community tanks.

Betta tank mates in 60 litres and above

This is where a true betta community tank becomes realistic.

You now have enough space for species to occupy different swim zones:

• Small rasboras (mid-water schooling fish)
• Small tetras like ember tetras
• Corydoras species (bottom dwellers)
• Snails and shrimp

Why it works:
At this size, territories form naturally. Fish can avoid each other, planting can create visual barriers, and the betta no longer feels constantly challenged.

This is the point where betta tank mates stop being risky and start being manageable.

Best Betta Tank Mates (Low Risk / Medium Risk / Avoid)

Not all “compatible” species are equal. Some are generally safe in most setups, others only work in very specific conditions, and some should be avoided entirely.

Low Risk (Generally Safe)

These species do not compete for territory and are ignored by most bettas.

Medium Risk (Situational)

These can work, but only with the right tank size, planting, and a calm betta.

Avoid (High Risk)

These species frequently trigger aggression, stress, or fin damage.

Which Fish Can Be Kept With Betta?

Very few fish species are reliably safe with bettas, and only when the tank is large enough to allow territorial separation.

In tanks under 40 litres, fish tank mates are usually a bad idea. Snails and sometimes shrimp are far safer choices. Once you reach 60 litres or more, small peaceful species that occupy different swim zones can work, such as pygmy corydoras (bottom dwellers), ember tetras, or chilli rasboras (mid-water schooling fish).

The key is not the species alone, but the combination of tank size, planting, and layout that allows fish to avoid the betta’s territory.

What Is the Best Fish to Pair With a Betta?

In smaller tanks, the honest answer is: none.

In nano and mid-size aquariums under 40 litres, the safest companions for a betta are actually snails, not fish. Snails do not compete for territory, do not trigger aggression, and help with algae control.

Fish tank mates only become realistic in larger setups of 60 litres or more, where peaceful species such as pygmy corydoras, ember tetras, or chilli rasboras have enough space to avoid the betta’s territory. Compatibility depends far more on tank size and layout than on the species itself.

What Animals Can I Put in My Betta Fish Tank?

A betta tank does not have to include only fish. In fact, in smaller aquariums, invertebrates are often far better companions than other fish.

Snails such as nerite, ramshorn, and mystery snails are the safest option because they do not compete for territory and are usually ignored by bettas. Shrimp can also work in planted tanks, although some bettas may hunt them. Very small peaceful fish should only be considered in larger tanks of 60 litres or more, where space and layout reduce aggression and improve compatibility.

Can Betta Fish Be in a Community Tank?

Yes, betta fish can live in a community tank, but only when the aquarium is large enough and carefully designed. In tanks of 60 litres or more, planting, hardscape, and clear separation of swim zones allow other peaceful species to avoid the betta’s territory. Small schooling fish such as ember tetras or chilli rasboras, along with bottom dwellers like pygmy corydoras, can work in these conditions. Most betta community tank failures happen in smaller tanks where there is not enough space, sight breaks, or proper introduction, which leads to stress and aggression.

Male Betta Tank Mates vs Female Betta Tank Mates

Male betta tank mates

Male bettas are highly territorial and tend to react strongly to movement in their space. They patrol the upper and middle parts of the tank and are more likely to chase or attack fish that resemble rivals or enter their territory. Because of this, male bettas require larger tanks, heavy planting, and careful species selection when kept with tank mates. In smaller tanks, males are usually best kept alone or only with snails.

Female betta tank mates

Female bettas are slightly more tolerant but are still territorial fish. They may coexist more peacefully with tank mates in medium to large tanks, but they still require proper layout, hiding spaces, and careful introduction. Females are not “community fish” by default, and the same rules about tank size and swim zones still apply.

Betta sororities

Betta sororities (keeping multiple females together) are advanced setups that require large tanks of at least 75–80 litres, heavy planting, and close monitoring. They are not recommended for beginners and should not be attempted as a solution for adding tank mates to a betta tank.

Tank Mates to Avoid With Bettas

Many compatibility problems happen not because people choose the wrong tank mates, but because they don’t know which species trigger betta aggression.

Bettas react strongly to fish that resemble rivals, move too quickly, or constantly invade their territory. Avoiding these species is just as important as choosing the right ones.

Avoid the following:

• Fin-nipping fish (such as tiger barbs)
  These species damage the betta’s fins and cause constant stress.
• Bright, long-finned fish (such as guppies)
  Bettas often mistake them for another betta and attack.
• Aggressive or territorial fish (such as angelfish)
  These compete for the same space and create conflict.
• Fast mid-water schooling fish in small tanks
  Constant movement stresses the betta and keeps it on alert.
• Any species that occupies the top and middle of the tank constantly
  This is the betta’s territory and leads to inevitable chasing.

Knowing what to avoid is often more important than knowing what can work.

How to Introduce Tank Mates to a Betta Tank

Even compatible species can fail if they are introduced the wrong way. Bettas are highly aware of changes in their environment and react strongly to new movement in their territory. The way you introduce tank mates often determines whether the setup works or ends in aggression.

Follow these steps to reduce stress and territorial behaviour:

1. Rearrange the decor before adding anything
   Changing the layout breaks existing territory lines and makes the tank feel “new” to the betta.
2. Turn the lights off
   Lower light reduces visual stimulation and initial aggression during introduction.
3. Add tank mates before reintroducing the betta (when possible)
   This prevents the betta from immediately claiming the entire tank as its territory.
4. Observe closely for the first 48 hours
   Watch for constant chasing, flaring, or fish hiding all the time.
5. Be ready to separate if needed
   Not every betta will tolerate tank mates, even in a perfect setup.

A calm introduction often makes the difference between a peaceful tank and a failed one.

Troubleshooting Betta Aggression

Even in well-planned setups, some bettas simply refuse to tolerate tank mates. Recognising the early signs of aggression is important because waiting too long often leads to injured fish and long-term stress in the tank.

Early signs of aggression

• Constant chasing of a specific fish around the tank
• Flaring repeatedly at the same tank mate
• Other fish hide all day and avoid open areas
• Fish showing signs of stress, such as clamped fins or rapid breathing

These are signs that the betta sees the tank mate as a territorial threat, not a companion.

What to do immediately

• Separate the fish as soon as possible
  Do not wait to see if the behaviour improves.
• Reassess the layout and stocking
  Check if there are enough hiding spots, plants, and swim zone separation.
• Accept that some bettas prefer to live alone
  Compatibility is never guaranteed, even in ideal tanks.

Acting quickly prevents injuries and allows you to redesign the setup before trying again.

Betta Tank Mate Compatibility Table

Realistic Stocking Examples (UK)

These examples show combinations that work in real UK aquariums when the tank is properly planted and laid out to break lines of sight and create clear swim zones.

30L setup

1 betta + 3 nerite snails

This is a safe and low-stress setup for a nano tank. The snails stay on surfaces and do not compete for territory, while helping with algae control. This is often the most realistic and successful combination for smaller betta tanks.

40L setup

1 betta + shrimp colony OR a small group of bottom dwellers (not both)

At 40 litres, you have just enough floor space to introduce either shrimp in a heavily planted tank or a very small group of bottom fish such as pygmy corydoras. Trying to combine both usually leads to overstocking and territorial stress.

60L setup

1 betta + 6 ember tetras + 6 pygmy corydoras + snails

This is where a true betta community tank becomes realistic. The tetras occupy the mid-water, the corydoras stay at the bottom, and the betta controls the upper space. With good planting and layout, territories form naturally, and aggression is greatly reduced.

FAQ

Can guppies live with bettas?

In most cases, no. Guppies have long, flowing fins that resemble those of another betta, which often triggers aggression. Even in larger tanks, bettas may chase or nip guppies constantly. In smaller tanks under 60 litres, this combination almost always leads to stress or injury. Guppies are one of the most commonly suggested, and most commonly failed, betta tank mates.

Can Corydoras live with bettas?

Yes, but only in larger tanks and with the right species. Small corydoras like pygmy corys can work well in tanks of 60 litres or more because they stay at the bottom and avoid the betta’s territory. They must be kept in groups and need plenty of floor space and hiding spots. In small tanks, they don’t have enough room to avoid conflict.

Do bettas prefer to live alone?

In small tanks, absolutely. Bettas are territorial by nature and do not need companions to be healthy or stimulated. In tanks under 40 litres, they are usually calmer and less stressed when kept alone. Tank mates are optional, not required, and should only be considered when tank size and layout make it realistic.

Can shrimp live with a betta in a 30L tank?

Sometimes, but you should expect losses. In a heavily planted 30L tank, shrimp can coexist if the betta has a calm temperament and plenty of visual barriers exist. However, many bettas will still hunt shrimp, especially smaller ones. Amano shrimp are usually safer than cherry shrimp due to their size.

What are unusual betta tank mates?

Snails and shrimp are often better companions for bettas than fish. Nerite snails, ramshorn snails, and mystery snails are ignored by most bettas and help with algae control. These “unusual” tank mates are actually the safest and most practical options for nano and mid-sized betta tanks. 

Can tetras live with bettas?

Yes, but only in larger tanks of 60 litres or more. Small, peaceful species such as ember tetras can work because they stay in the mid-water and move calmly in groups. In smaller tanks, their constant movement can stress the betta and trigger territorial behaviour.

How many tank mates can a betta have?

This depends entirely on tank size and layout. In tanks under 40 litres, a betta should usually only have snails or shrimp. In 60 litres and above, small groups of peaceful fish can be added, but overstocking quickly leads to stress and aggression. Fewer tank mates almost always lead to better results.

Conclusion: The Truth About Betta Tank Mates

The reason there is so much conflicting advice about betta tank mates is simple: most guides ignore tank size, tank layout, and how bettas actually behave in real aquariums.

In typical UK tanks of 20–40 litres, bettas are usually calmer and healthier when kept alone or only with snails. These conclusions follow modern welfare guidance and years of observing what actually works for UK betta keepers in real homes. Trying to force a community tank into a nano setup is the main cause of aggression, stress, and failed combinations.

Once you reach 60 litres and design the aquarium with heavy planting, hiding places, and clear swim zones, peaceful tank mates become realistic. Even then, success depends more on layout and introduction method than on the species itself.

If you remember one thing from this guide, let it be this:

Tank mates are optional. A healthy, calm betta in the right tank is always the priority.

When you do choose tank mates, base your decisions on litres, risk, and realism, not on generic online lists.

If you’re still setting up your tank, choosing the right size and layout is the most important first step before considering any companions.

Guide written by the AquaticsHub team – UK-based aquarists focused on practical, welfare-first fishkeeping.