How Many Platies In a 20 Gallon Tank (80 Liters) Should You Have? - "Platies" by crschmidt is licensed under CC BY 2.0.
How Many Platies In a 20 Gallon Tank (80 Liters) Should You Have? - "Platies" by crschmidt is licensed under CC BY 2.0.


When setting up an aquarium, one of the most common questions asked by enthusiasts is, “How many platies in a 20 gallon tank (80 liters) can I comfortably keep?” This question is crucial as it touches on the well-being of the fish and the ecological balance of the aquarium. Platies are colorful, friendly, and active fish that make a great addition to many freshwater tanks. They are known for their ease of care, making them ideal for both novice and experienced aquarists. However, understanding the right number of platies for a 20-gallon tank (80 liters) is essential to ensure they have enough space to thrive without overcrowding. In this guide, we will explore the factors that influence how many platies you can keep in a 20-gallon (80 liter) tank, including considerations for their breeding habits, tank mates, and general care requirements to ensure a healthy and vibrant aquarium.

About Platies

Platies are a popular freshwater fish among aquarists, known for their bright colors and easy care. They belong to the genus Xiphophorus, which includes several species, but the most common in aquariums is Xiphophorus maculatus, also known as the Southern Platyfish or Common Platy.


Platies are small, laterally flattened fish that usually grow to about 2 to 2.5 inches (5 to 6,5 cm) in length. They have a wide variety of colors and patterns, including red, orange, yellow, blue, and black, often with spots or streaks. Some of the most popular color varieties include the Red Platy, Sunset Platy, and Tuxedo Platy. Their bodies can be either solid colored or have a combination of colors, and breeders have developed many hybrid varieties to enhance their aesthetic appeal.

Their fins are small and rounded, with the males having a more pointed anal fin known as a gonopodium, which is used for reproduction. Females are generally larger and have a more rounded body shape compared to males.


Platies are known for their peaceful temperament, making them an excellent choice for community aquariums. They are active swimmers and tend to occupy the middle levels of the water column in an aquarium. Platies are schooling fish, so they thrive in groups and exhibit more natural behavior when kept with others of their kind. A group of five or more is ideal to see them at their best, with a good mix of males and females to promote social interaction.

Platies are omnivores and will accept a wide variety of foods, including flake food, frozen, and live foods. Their diet can include plant matter as well as small crustaceans and insects.


Platies are livebearers, meaning they give birth to free-swimming fry rather than laying eggs. They are prolific breeders, and the females can give birth to a batch of fry every 4 to 6 weeks. The fry are relatively large and can be raised on finely ground flake food or specially formulated fry food. Care should be taken to provide hiding spots for the fry, as adult fish may eat them if given the chance.

Overall, platies are hardy, adaptable, and colorful fish that can add life and color to a community aquarium. Their easy care and peaceful nature make them a favorite among both beginner and experienced aquarists.

How Many Platies In a 20 Gallon Tank (80 Liters)?

When considering how many platies in a 20-gallon tank (80 liters) you can keep, it’s important to factor in not just the immediate space requirements but also the potential for population growth due to their prolific breeding habits. Platies are, as mentioned, livebearers, meaning they give birth to free-swimming fry rather than laying eggs. A single pair of platies can produce dozens of fry in a short period, potentially leading to overcrowding if not managed properly.

For a 20-gallon tank (80 liters), a good starting point is to stock with a small group of platies, typically around 5 to 6 adult fish. This allows enough space for each fish to swim freely and exhibit natural behaviors without excessive competition for resources. However, considering their breeding rate, this number can quickly increase if the fry are allowed to grow to adulthood within the same tank.

To manage the population increase from fry, there are a few strategies you can employ:

  • Separate the Fry: If possible, remove the fry to a separate grow-out tank where they can be raised until they’re large enough to be rehomed or sold. This prevents the main tank from becoming overcrowded and ensures the fry receive appropriate care.
  • Predation: In a community tank, having larger fish that will naturally predate on the fry can help control the population. However, this should be approached with caution to ensure a balanced ecosystem and that the tank mates are compatible with platies.
  • Rehoming: Regularly rehoming the fry to other aquarists or local fish stores can help manage the population within your tank.

When selecting tank mates for platies in a 20-gallon setup (80 liters), choose peaceful species that thrive in similar water conditions. Suitable tank mates include small tetras, peaceful barbs, dwarf gouramis, and other livebearers like mollies and guppies. Avoid aggressive fish or those large enough to see platies as prey.

Remember, the key to a healthy and balanced aquarium is not just about the number of fish but also about maintaining good water quality, providing a varied diet, and ensuring the tank is well-planted with hiding spots for fry and shy fish. Regular water changes, monitoring water parameters, and adjusting the stock levels as necessary will help keep your platies and their tank mates happy and healthy.

How Many Platies In a 20 Gallon Tank (80 Liters) Should You Have? - "Platies" by crschmidt is licensed under CC BY 2.0.
How Many Platies In a 20 Gallon Tank (80 Liters) Should You Have? – “Platies” by crschmidt is licensed under CC BY 2.0.

Setting Up a 20 Gallon (80 Liters) Platy Tank

Setting up a 20-gallon tank (80 liters) for platies involves creating a balanced and healthy environment that caters to their needs. Platies are vibrant, active, and hardy fish that require a well-maintained tank to thrive. Here’s a step-by-step guide to setting up an ideal habitat for them:

Tank Selection

  • Ensure the tank is at least 20 gallons. This size provides ample space for a small group of platies and potential tank mates, as well as room for swimming and exploration.

Substrate and Decoration

  • Choose a soft, fine substrate like sand or smooth gravel to avoid injuring the platies.
  • Add plants, both live and artificial, to provide hiding spots and mimic their natural environment. Live plants also help maintain water quality by absorbing nitrates.
  • Incorporate decorations like driftwood, rocks, and caves to create a visually appealing setup and additional hiding places for the fish.


  • Install a reliable filtration system that can handle the bioload of a fully stocked tank without creating too strong of a current, as platies prefer relatively calm waters.
  • A sponge filter or a hang-on-back (HOB) filter with adjustable flow is a good choice for platies.

Heating and Lighting

  • Maintain the water temperature between 72°F and 78°F (22°C to 26°C). Use an aquarium heater with a thermostat to keep the temperature stable.
  • Provide moderate lighting to support plant growth without encouraging excessive algae. Around 8-10 hours of light per day is sufficient.

Water Parameters

  • Keep the water pH between 7.0 and 8.2. Platies are adaptable but prefer slightly alkaline conditions.
  • Ensure the water is well-oxygenated. While the filtration system usually provides enough water movement for oxygen exchange, an air stone can add extra oxygenation if needed.

Cycling the Tank

  • Before introducing platies, cycle the tank to establish beneficial bacteria. This process usually takes a few weeks and involves setting up the tank, running the filter, heater, and aerator (if used), and monitoring water parameters until ammonia and nitrites are undetectable, and nitrates are at a safe level.

Adding the Platies

  • Once the tank is fully cycled and water parameters are stable, gradually introduce the platies to their new home. Acclimate them slowly to avoid shock by floating their bag in the tank water and gradually mixing tank water into the bag over an hour.


  • Perform regular maintenance, including weekly water changes of 10-20% to remove toxins and replenish minerals.


  • Feed a varied diet consisting of high-quality flake food, frozen, or live foods such as brine shrimp or daphnia. Feed small amounts 1-2 times daily, only as much as they can consume in a few minutes to avoid overfeeding.

By following these steps, you’ll create a thriving environment for your platies, supporting their health and well-being in your 20-gallon (80 liter) tank.


In conclusion, when considering how many platies in a 20 gallon tank (80 liters) you can keep, it’s important to start with a manageable number, such as 5 to 6 adults, to ensure the well-being of each fish. This initial number takes into account not only the space required for the fish to live comfortably but also the potential increase in population due to their prolific breeding. Proper tank setup, regular maintenance, and a responsible approach to managing fry production are key to maintaining a healthy balance in your aquarium. By following these guidelines, you can enjoy the lively presence of platies in your 20-gallon tank (80 liters), creating a thriving aquatic environment that is both enjoyable to watch and easy to manage.