What is the best size tank for a betta fish?

Choosing the best size tank for a betta fish is a critical first step towards having a happy and healthy fish. Choose the wrong size and your fish may be doomed.

How Big Should A Betta Tank Be?

The short answer is: The best size tank for a single Betta Fish is 5 gallons up to even 10 gallons. A Betta can survive in a 2.5 gallon tank but we do not recommend any smaller for a number of reasons. If you plan on adding more fish to the tank then start with at least a 10-15 gallon tank.

This may seem counter-intuitive since you see Betta fish stored in small cups while at the pet store. But this isn’t because they like being confined to small spaces….

Betta Fish are know as Japanese Fighting Fish – so yes they like to fight – especially the males.┬áSo think of those small cups more as “solitary confinement” vs “ideal tank size”.

If you are interested in why you need a tank at least 5 gallons keep reading!

Reason #1: More stable water conditions

Your fish tank is not only home to your fish, but also the place where it is fed as well as needs to go to the bathroom.

Picture a small house where you are forced to sleep in the kitchen and there’s a toilet in the corner – that’s the equivalent of an unfiltered fish bowl. Except its not filling with trash, its filling with ammonia and other toxins will kill your fish over time.

Or picture a spacious house where you have your own bedroom with a spacious master bath – that’s a 5 gallon tank with a filter!

Which do you think will stay cleaner longer and be more enjoyable to live in?

The larger house (i.e. tank) of course.

Simply put, the amount of waste produced by your Betta Fish as well as waste from any uneaten food will make your tank water quickly unstable and unhealthy in a smaller tank.

On the other hand, a larger tank takes much longer to get dirty based on the same amount of waste. This means cleaner water for longer periods of time and less frequent water changes.

Reason #2: Larger Tanks Support Filters

Another must-have in your Betta Fish tank is a filter!

Simply put a filter helps keep your water clean longer, which means a healthier fish and less frequent water changes.

Small 1 gallon tanks or bowl simply do not come with a filter nor are built to support one.

Larger tanks like a 2.5 to 5 gallon tanks frequently come with filters or are built to support one if purchased separately.

Reason #3: Larger Tanks Support Heaters

Betta Fish are tropical fish that in order to thrive need a consistent water temperature of 78-82 degrees.

If your house is consistently those temperatures then you don’t need a heater.

If you are like the rest of us you need a heater. Especially if you live in the Northeast where we turn the heat on based on the calendar not outdoor temperature (see if you can hold out till Nov 1st)!

In order to add a heater to your tank you generally need a larger tank with room to hang the heater on (along with the filter that is also needed).

So you need a larger tank with a heater, won’t fit or work in a bowl

Reason #4: Room to Move

It might not be obvious from what you see in the pet store with the poor Betta Fish sitting in cups by themselves, but they actually have quite a personality.

Give them some room to move and they will flourish.

Stick them in a slightly larger bowl than they were in the pet store and the will be BORED.

Betta Fish, like the rest of us, need exercise – room to move as well as mental stimulation along the way.

Reason #5: Plenty of room for plants and decorations

Natural plants in your tank will not only look cool, but they actually help keep the water cleaner over time.

Also adding some very cool decorations to your tank will make it mentally stimulating for your Betta.

Reason #6: Room for Tank Mates

Betta Fish in some cases can be paired with tank mates. But before attempting to add any other fish to your tank please read up on it.

Otherwise those new fish might be dinner for your Betta Fish!

Just keep in mind the larger the tank the more potential to add tank mates.

More things to look for in a tank:

Size IS important, but isn’t everything when it comes to Betta Fish tanks. There’s a few more things you want to consider when shopping for an aquarium for your Betta Fish:

Wide Tank vs Tall Tank

In their natural habitat Betta Fish live in shallow pools and can even come to the surface to breath air.

That’s right – they can breath air for short periods of time due to a having a labyrinth organ.

So Betta Fish prefer to not have to journey too far to get to the surface, ideally you find a tank that is more wide than tall – which is common with many larger tanks that they quickly grow in width before height.

So choose a wider tank with plenty of surface area, not a deep tank.

Not only does this make life much easier on your Betta, is far easier to add plants and decorations to a wide tank vs a tall tank.

Lights and Lids

Your tank should have a lid on it that contains a light. The light will not just brighten up your tank but a good LED or fluorescent light is need to help any natural plants grow.

The lid is important not just to hold the light, but to keep your Betta from jumping out of the the thank.

That’s right – they jump.

In fact we lost our first Betta while away for the weekend and our neighbor was taking care of it. She saw something stuck to the floor….turned out it wasn’t leaf it was our fish.

So keep a lid on it and you could very well be saving your Betta Fish from an untimely death.


Hopefully we’ve convinced you that a larger tank like a 5 gallon is the way to go.

When it comes down to it, your Betta fish just really needs these to survive

  • clean water
  • warm water
  • food
  • mental stimulation

This is far easier to produce in a 5 gallon tank vs a smaller tank or a bowl.

You may save money buying a smaller tank, but you are creating more work for yourself and poor living conditions for your betta fish.

So buy a 5 gallon tank! Not sure which one to buy?

See our article: The Best Betta Fish Tanks By Price : A Buyers Guide

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