How Many Platies in a 55-Gallon Tank?

You can keep between 18 to 20 platies in a 55-gallon tank, but there are a lot of factors to consider including fish size, activity level, gender, and decorations.

Adding the right number of fish to the tank will allow them to grow healthily, so your platies will be in perfect health if the tank is big enough. Moreover, this will eliminate any risk of aggression in the aquarium.

Platies are interesting and fun fish because they’re hardy, peaceful, and ideal for beginners. This is why they’re among the most popular fish species to choose from if you’re getting pet fish for the first time.

The platy fish come in various colors, so might be tempted to add more. Keep on reading to learn about the right number of fish to add to the tank.

How Many Platies in a 55-Gallon Tank?

Every platy fish needs about 4 liters of water to stay healthy. So, even if you are keeping a single platy fish alone, a 10-gallon tank won’t work because these fish need a tank with lots of live plants.

Even though platies aren’t schooling fish, they love living in groups, so a group of 5 fish can live happily in a 10-gallon tank, although it might be too crowded. For a 55-gallon tank, you should limit the number of fish to 20 platies, as this will give the fish space to play and swim comfortably.

Platies aren’t aggressive, but they’re extremely active and need room to roam freely. Male fish are smaller than females, as the adult males can grow up to 1.5 inches, while the females can grow up to 2.5 inches.

School of Neon Blue Platies

Number of Platies Based on the Size of the Tank

Not only are platies peaceful and easy to care for fish, but they’ll also be the perfect tank mates to any other freshwater fish that you have the same tank requirements. Here’s the number of fish to keep in different tank sizes.

Less than 10 Gallons

This tank will be too small for platies. Keeping a single platy fish in the tank is possible but not recommended because these creatures are sociable fish that love to live in groups.

Moreover, a smaller tank is subject to pH fluctuations and toxic materials will accumulate, eventually affecting the health of the platies.

10-Gallon Tank

This tank will be big enough for a male and a female. In the right conditions, the fish will breed and give birth to multiple baby fish. However, you’ll need to upgrade after the birth of the baby platies to allow for proper gas exchange.

Between 10 and 20-Gallon Tank

A 20-gallon tank will be big enough to support up to eight platies, especially if they haven’t reached maturity. However, this doesn’t mean that you should add more male platies because they’re smaller.

As a matter of fact, a tank with a capacity of less than 20 gallons will be too crowded because you need to add more aquatic plants to provide the fish with enough hiding spots.

Between 21–40 Gallon Tank

This tank will be big enough for up to 12 platies. Due to the bigger size of the aquarium, it will require less maintenance, so this is an excellent choice for a novice aquarist.

40-Gallon Tank or Bigger

A bigger tank is an excellent choice for setting up a diverse community of various colorful fish. However, you need to make sure that the different fish species living in the tank are of the same temperament, so they won’t attack each other.

Larger tanks are more difficult to maintain and require more attention. Nevertheless, they’ll be the perfect choice when the family of your pet fish is growing.

What Factors Affect the Number of Platies in the Tank?

As you increase the tank size, you shouldn’t just multiply the number of fish in the tank. Platies prefer to swim in the middle of the tank, usually hiding between the leaves.

So before you add more fish to your tank, you need to make sure that you’re setting up a healthy aquarium where the fish will thrive. Here are some factors to consider before adding more fish.


Before you add more fish to your aquarium, make sure that they’ve reached maturity. Otherwise, your tank will be too crowded when your platies reach adulthood.

The tank should be big enough to support all the fish, while they’re swimming and interacting peacefully. If the aquarium is too crowded, these fish will start to act aggressively and attack each other, despite their peaceful nature.

Activity Level

Even though platies are peaceful fish, they’re pretty active. So, you need to make sure that the tank is big enough for all the fish to feed comfortably and explore the tank without feeling too restricted.

Platy in Freshwater Aquarium


In addition to the number in the tank, you need to maintain a healthy ratio between males and females. Male platies are likely to be more aggressive, especially when food is scarce or the tank is too crowded.

At the same time, when there are too many male fish in the aquarium, they can stress out the females as they compete for mating.

Social Behavior

Platies prefer to live in groups, but they’re not schooling fish. Although they’d appreciate being within a group of their own kind or another compatible species, they appreciate having some space.

The tank should be big enough for a group of platies to feed, play, and breed without feeling too restricted.

Live Plants and Decorations

Live plants make the aquarium a happy place for platies because their natural habitat is rich in vegetation. At the same time, these plants provide perfect hiding spots to keep the fish happy and confident.

Without enough aquatic plants, the tank won’t be suitable for platies, even if it’s big enough. So, you need to think about moving some fish to a new tank, if there’s no space to plant enough live plants in the aquarium.

At the same time, you need to put enough rocks and decorations as they’ll provide platies with more hiding spots.

Have Another Tank Size You’re Looking for?

How Many Platies in a 5-Gallon Tank?

How Many Platies in a 10-Gallon Tank?

How Many Platies in a 20-Gallon Tank?

How Many Platies in a 29- Gallon Tank?

Wrap Up

A 55-gallon tank is big enough to support between 18 and 20 platies. However, you need to make sure that there are enough aquatic plants and hiding spots to keep the fish happy and healthy.