One of the things that make betta fish the most popular tropical fish in the world is that you can keep them in a small tank. But we mustn’t exploit bettas for their modest spatial requirements!
A 5-gallon tank is the very minimum tank size for a single male betta splendens, and they should never be kept in fish bowls or anything smaller. Although female betta fish can sometimes be kept in groups, a 5-gallon tank is far too small for that.
Let’s take a closer look at a betta fish’s tank size requirements, and also which tank mates you can consider for a 5-gallon nano tank.
Why You Should Never Keep Male Betta Fish Together
Male betta splendens are so aggressive, they’ve even earned themselves the fearsome name ‘Siamese fighting fish’. In Asia, they are sometimes pitted against each other in cruel contests where the fish fight to the death.
If you were to keep two males in the same tank, they’d almost certainly kill or severely damage each other.
To overcome this problem, some people have created divided betta tanks. Using some type of permeable barrier such as a fine mesh, or porous acrylic, the fish are kept in separate chambers.
But tank dividers have many issues associated with them, and is a 5-gallon tank big enough for a divider anyway?
Is a 5-gallon Divided Tank Big Enough for Two Male Betta Fish?
The simple answer to this question is: No!
Although some aquarium brands have created divided 5-gallon tanks for two bettas, or 10-gallon tanks for 3 bettas, in reality, the chambers in these tanks are far too small for your bettas to be healthy and happy.
Also, check out my take on the issues with betta tank dividers, and how to do it right in 10-gallon tanks here.
How Much Swimming Space Does Each Betta Fish Need?
Male betta fish need a minimum of 5 gallons of swimming space each. To give them any less is cruel and risks causing them great stress, health problems, and premature death.
Betta fish should never be kept in fish bowls, or tiny 3-gallon tanks that are sometimes sold irresponsibly.
Female bettas are slightly smaller and less territorial, but I’d still advise giving each fish at least 4 gallons of swimming space.
Do I Need to Filter a 5-Gallon Betta Tank?
Yes! In fact, effective filtration is especially important for small tanks because water quality is less stable in smaller tanks than in larger ones. You also need to avoid overfeeding, clean the gravel and make partial water changes regularly.
Because betta fish don’t like strong currents, I’d recommend sponge filters for 5-gallon tanks. You can check out our top picks of such filters here.
Why You Should Never Keep Male and Female Betta Fish Together
Although male and female betta fish need to be kept together for a brief period for breeding, they should never be kept together for the long term.
This is because male betta fish can be incredibly aggressive towards females, and may attack them before, during, or after mating.
Aggression can be so pronounced that there is never any guarantee that mating will be successful. That’s why breeding bettas is best left to experienced fish keepers and professionals!
Is a 5-gallon Tank Big Enough for Breeding Bettas?
Breeding bettas is best left to pros, but in case you’re wondering – a 5-gallon size tank is too small to breed betta fish.
Since female betta fish can lay several hundred eggs, a 10 or 20-gallon tank capacity is much preferable!
Can You Keep Female Betta Fish Together?
Female betta fish can sometimes be kept together successfully. The term used in the hobby for an all-female betta tank is a ‘betta sorority’. But betta sororities are not always the harmonious setup that people hope for.
Like male betta fish, females can be quite aggressive with their female friends as well as other fish species, and will often fight or quarrel with one another. That’s why each female needs plenty of hiding places and enough swimming space.
Is a 5-gallon Tank Big Enough for a Betta Sorority?
As we discovered a moment ago, each female betta deserves at least 4 gallons of swimming space each – that’s why a 5-gallon aquarium is far too small for multiple female bettas!
Can You Keep Two Female Betta Fish Together?
So, if each female betta needs 4 gallons of swimming space, you could keep two of them in a 10-gallon tank, right?
Well, not quite. Female bettas should never be kept in pairs because the dominant fish will nearly always intimidate, or attack the more submissive fish.
To overcome this issue, female bettas need to be kept in larger groups of at least 5 fish in a larger tank. This way territorial behavior will be dispersed more evenly among several fish. With luck, none of the females will get bullied excessively, and a relatively harmonious environment can ensue.
What’s the Minimum Tank Size for a Betta Sorority?
You’ve probably done the math by now. If each female betta needs 4 gallons of swimming space, and the minimum number to keep is 5 fish, you’ll need a minimum of a 20-gallon fish tank to keep them successfully.
Even better would be to keep them in a 30-gallon tank with some clean-up crew tank mates, such as corydoras catfish, freshwater shrimp, or snails. The extra diversity will bring much more interest to the tank, and the additional tank mates will also help to keep the aquarium clean, improving water conditions.
Betta Tank Mates for a 5-gallon Aquarium
Since 5 gallons is the absolute minimum tank size for a betta fish, your options are limited when it comes to adding tank mates.
Only the very smallest and solitary tank mates are going to be feasible without crowding out the tank, and here I’m talking chiefly about invertebrates.
Freshwater Aquarium Shrimp
Some of the best tank mates for betta fish in small tanks are the various freshwater shrimp species. The 3 most popular shrimp to keep with betta fish are: Amano shrimp, ghost shrimp, and cherry shrimp.
All three of these shrimp are peaceful and hardy, and do an excellent job of cleaning up algae and leftover fish food. The only issue with ghost shrimp and cherry shrimp is that they like to breed in freshwater and can easily overpopulate an aquarium – especially a 5-gallon nano tank!
Amano shrimp, on the other hand, don’t breed in freshwater so will never overcrowd your tank. They also have a reputation for being the very best algae eater of them all!
Additionally, Amano shrimp are slightly larger than cherry or ghost shrimp, so are better equipped to fend off any menacing attacks from an aggressive betta fish!
Freshwater Aquarium Snails
Aquarium snails are another extremely popular choice for small betta tanks. Just like shrimp, they do an outstanding job at cleaning up detritus and algae to keep the water quality high. Among the most popular snail species for betta tanks are nerite snails, mystery snails, and ramshorn snails.
But extreme caution is advised when choosing snail tank mates for your betta! Some snail species will eat aquarium plants, and many of them will breed prolifically in freshwater, meaning your tank will quickly get overpopulated.
For this reason, I wouldn’t recommend ramshorn snails, Malaysian trumpet snails, or mystery snails for a 5-gallon tank. All of these species can multiply so rapidly that you’re likely to have a snail epidemic on your hands very quickly!
Betta Fish Aggression with Tank Mates
While male betta fish will always fight with each other, many will behave quite peacefully towards other tank mates, such as shrimp and snails.
It must be noted, though, that this varies considerably between individuals! While one male betta will barely notice the presence of shrimp and snails in his tank, others will make it their mission to wipe out every other living thing in their environment.
Most of the time, bettas will get along fine with aquarium invertebrates, but due to their quirks, harmony is never 100% guaranteed!
Keeping Other Fish with Bettas in a 5-gallon Tank
I can’t think of any fish species that I’d recommend keeping with a betta in a five-gallon tank.
While tiny fish species like neon tetra, rasboras, or cory catfish could theoretically fit into a 5-gallon tank with a single betta, these are all schooling fish that require the presence of several members of their own kind to feel safe and happy.
Just keeping one or two of these types of fish will result in them becoming miserable and almost certainly dying young from health problems.
Keeping Other Fish with Bettas in a 10-gallon Tank
To see my suggestions for betta tank mates for a male betta in a 10-gallon tank, check out my article on 10-gallon betta fish tanks here.
I’ll tell you now though, that for most mid-surface level schooling fish, I’d recommend a minimum size of a 20-gallon aquarium.
A 5-gallon tank is just about big enough for a single male betta fish, but not big enough to divide the tank or to keep other fish as tank mates.
You could also keep a solitary female betta in a 5-gallon betta fish tank, but certainly not more than one. Female sororities require at least 5 individuals to remain harmonious, and for that, you’ll need at least a 20-gallon aquarium.