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How Many Zebra Danios in a 10-gallon Tank?

Zebra danios (also known as striped danios or zebrafish) are a type of freshwater fish and highly popular with aquarium hobbyists. A hardy, charismatic fish, this species is easy to care for and makes a great addition to any aquarium. But how many can you keep in a 10-gallon tank, for example?

Zebra danios are an active fish and need space to swim about freely. As a type of shoaling fish, they should be kept in groups. For a 10-gallon tank, I recommend 5 danios (1 male and 4 females, if possible) as any more than that and the tank will quickly become ‘cramped.’

Now that you know you can keep up to 5 zebra danios in a 10-gallon tank, let’s explore this topic further. I’ll explain why zebra danios prefer larger and longer tanks; if they’re prone to aggressive behavior; what happens to them in both an underpopulated and overcrowded aquarium; whether or not you can keep them in smaller tanks such as the 3- or 5-gallon versions; and what type of water conditions they prefer.

So, if you’re ready to learn more, then let’s dive deeper into the exciting aquatic world of the zebra danio fish!

How Many Zebra Danios should be Kept Together?

Zebra danios are a social or shoaling fish and prefer the company of their own kind. How many you should keep is dependent on the size of your tank. The recommended number is no less than 5 danios since they thrive in groups.

That said, you must ensure your aquarium is conducive to the active nature of this species. Larger, longer tanks are better and will allow enough space for fish to swim about freely and explore their aquatic environment.

Zebra danios that aren’t kept in big enough groups (5 or preferably more), will often become anxious and may even exhibit aggressive behavior towards each other and other fish in a captive environment. This increase in stress will ultimately affect the overall health of your tank over time.

How Many Zebra Danios can I Keep in a 5-gallon Tank?

Zebra danios are an active, social fish that like to be kept together in larger numbers. Because they do better in groups of 5 or more, they shouldn’t be kept in a 5-gallon tank as it’s just too small to accommodate their vigorous nature.

If 5 or more zebra danios are confined to an aquarium less than 10-gallons, you run the risk of excessive nitrate build-up in the tank. This can make your fish ill and ultimately cause death. Bigger is always better when it comes to tank size for zebra danios (and basically any fish in captivity, for that matter)!

zebra danios

How Many Zebra Danios can I Keep in a 3-gallon Tank?

The only time you should keep zebra danios in a 3-gallon tank is if it’s a nursing tank for baby fry. A 3- or even 5-gallon aquarium also works well as a hospital or ‘sick’ tank for ill zebra danios to recover in. This small of a tank should only be used on a temporary basis with young or ailing zebra danios being moved to a larger tank as soon as they’re physically able.

What is the Best Size Tank for Zebra Danios?

When it comes to tank size for zebra danios, bigger is better. As a type of shoaling fish, this species thrives in larger groups of 5 or more. Therefore, they need to be kept in a large tank that’s longer rather than taller.

A 20-gallon tank or bigger is ideal for 5 zebra danios. This allows the fish enough space to swim about freely with each other and become familiar their aquatic surroundings. This also helps reduce the risk of ammonia poisoning due to overcrowding or nitrate build-up.

What Happens if Zebra Danios are Kept in Too Small of a Tank?

Overcrowding an aquarium is one of the leading causes of fish aggression. For a species like zebra danios that like to swim about with others of their kind and need space to freely explore their surroundings, a tank that’s too small will increase stress and tension. This can ultimately lead to illness and even death.

The general rule of thumb for stocking an aquarium is 1 inch of fish per gallon of water. Since the average zebra danio grows up to 2 inches in length and you should keep at least 5 together at any given time, you would need at least a 10-gallon tank to house them.

Is 3 Zebra Danios enough?

In my opinion as an experienced aquarium hobbyist and fish lover, 3 zebra danios in a tank (no matter the size) are not enough. Shoaling fish are social creatures and need the company of other ‘like fish’ to not only survive but thrive in a captive environment. For their true outgoing and active nature to come alive, they need to be in a group of 5 (at the very least)!

Are Zebra Danios Aggressive?

In general, zebra danios aren’t aggressive, provided they’re kept in larger groups in a big enough tank. Overcrowding increases stress and tension in a captive aquatic environment. An aquarium with an adequate amount of longitudinal space gives zebra danios the room they need to race about the tank! Therefore, ensure your aquarium is at least 20-gallons (or more) for a shoal of at least 5 zebra danios.

Why are My Danios Chasing Each Other?

Zebra danios will often chase each other in a captive aquatic environment. As a highly active fish, they seem to enjoy endless games of ‘tag’ as they race around the tank together. This action is innate to this species and not cause for alarm unless you notice other aggressive conduct such as fin nipping.

Chasing each other is also a sign of spawning behavior for zebra danios. Males will often pursue females during the breeding season. Though it may look aggressive, it’s natural for this type of fish when they’re trying to mate.

It’s important to note that zebra danios in an underpopulated tank may resort to predatory actions – such as chasing and nipping fins of lower ranking fish. If you notice this behavior, then you need to either add more zebra danios to your aquarium or quarantine the aggressors for a period of time.

Check out these hang-on quarantine nets for aggressive fish available online through Amazon.

What Type of Water Conditions do Zebra Danios Prefer?

Apart from a large tank, zebra danios need proper care to not only survive but thrive in captivity. The water parameters must be conducive to this freshwater species and include a regulated temperature between 65-and 77-degrees Fahrenheit with a pH range of 6.5 to 7.2.

Regarding filtration, zebra danios aren’t demanding and therefore standard equipment is fine. If you can invest in a HOB filter, I recommend you do as it provides a faster moving current which this species likes to swim through and play in!

Regular partial water changes are a must to keep the aquatic environment healthy and safe for zebra danios (as well as all other aquarium inhabitants). Removing 10-15% of the existing liquid and replacing it with clean, treated tap water weekly will go a long way in reducing the risk of toxic ammonia build-up.

And since zebra danios are active swimmers who can ‘jump’ out of water, it’s best to keep them in a tank with a cover or lid. Otherwise, you may come home one day to find the unthinkable – your beloved fish lying dead on the floor!


To conclude, zebra danios are an energetic fish that need plenty of room to swim freely in an aquarium. They’re the perfect example of a shoaling fish which are friendly and need others of their kind to thrive in a community tank environment. They should be kept in groups of 5 (if possible) in a 10-gallon tank – at the very least – as anything smaller will quickly become ‘cramped.’

Hopefully, this article has answered your questions regarding zebra danios, how many to keep, and how to care for them. Thanks for reading and good luck with your aquarium hobby!

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