20 Gallon Guppy Tank (80 Liters) – How To Set It Up - "Male Guppy" by Mihnea Stanciu is licensed under CC BY 2.0.
20 Gallon Guppy Tank (80 Liters) – How To Set It Up - "Male Guppy" by Mihnea Stanciu is licensed under CC BY 2.0.


Setting up a 20 gallon guppy tank (80 liters) is an exciting journey into the vibrant world of aquarium keeping. Guppies, with their dazzling colors and lively behavior, make an ideal choice for both novice and experienced aquarists looking to create a dynamic underwater landscape. A 20 gallon tank (80 liters) offers ample space for these small, yet active fish to thrive, allowing for a beautifully curated community of guppies and compatible tank mates. This guide aims to provide you with the essential steps and considerations for establishing a healthy and visually appealing 20 gallon guppy tank (80 liters), ensuring a harmonious environment for your aquatic pets.

Appearance and Behavior

Guppies (Poecilia reticulata), often celebrated for their vibrant colors and dynamic social behaviors, are a popular freshwater fish species in the aquarium hobby. Here’s an overview of their appearance and behavior:


  • Size and Shape: Guppies are relatively small fish, with males typically reaching up to about 4 centimeters (1.5 inches) in length and females being slightly larger, up to about 6 centimeters (2.5 inches). They have slender bodies with a tapered head and a wide, fan-shaped tail.
  • Color and Patterns: Guppies are known for their extraordinary range of colors and patterns. Males, in particular, display a wide array of vibrant hues such as red, blue, green, yellow, and orange, often combined with various patterns like spots, stripes, and patches. Females are usually less colorful, with more subdued shades and fewer patterns.
  • Sexual Dimorphism: There is a pronounced difference between males and females. Males are smaller but more brightly colored and have larger, more ornate tail fins compared to females, which are larger, have rounder bodies, and are less brightly colored.


  • Social Behavior: Guppies are generally peaceful and sociable fish that do well in community tanks. They exhibit schooling behavior, especially when kept in groups, which helps reduce stress and predatory threats.
  • Breeding: Guppies are livebearers, meaning they give birth to free-swimming fry rather than laying eggs. They are prolific breeders with a gestation period of about 28 to 30 days. Females can store sperm and give birth multiple times from a single fertilization.
  • Feeding: They are omnivores and not particularly picky eaters. In the wild, their diet consists of algae, small invertebrates, and detritus. In aquarium settings, they thrive on a diet of high-quality flake food, supplemented with frozen or live foods such as brine shrimp or daphnia.

How To Set Up A 20 Gallon Guppy Tank (80 Liters)

Setting up a 20 gallon tank for guppies (80 liters) involves creating a safe, healthy, and stimulating environment that mimics their natural habitat as closely as possible. Guppies are hardy fish, but they thrive in well-maintained tanks with specific conditions. Here’s a guide to setting up a 20 gallon guppy tank (80 liters):

Tank Preparation

  • Choose a Location: Place the tank in a stable, level spot away from direct sunlight, drafts, and heat sources to prevent temperature fluctuations.
  • Tank Size: A 20-gallon tank (80 liter) is an excellent size for guppies, allowing for a healthy community with space for swimming and territories. It can accommodate a small group of guppies along with potential tank mates.

Filtration and Aeration

  • Filtration System: Install a reliable filtration system to keep the water clean and oxygen-rich. Guppies do well with sponge filters or hang-on-back filters, which provide gentle water flow and filtration without creating strong currents.
  • Aeration: While the filtration system often provides sufficient water movement for gas exchange, an air pump with an air stone can add additional aeration if needed, especially in densely stocked tanks.

Water Conditions

  • Temperature: Maintain the water temperature between 22°C to 28°C (72°F to 82°F). Use an aquarium heater with a thermostat to keep the temperature stable.
  • pH Level: The ideal pH level for guppies is between 6.8 and 7.8.

Substrate and Decorations

  • Substrate: Choose a substrate that complements the aquarium’s aesthetics. Sand or fine gravel works well for guppies.
  • Plants: Add live plants such as Java fern, Anubias, or Hornwort. Plants provide hiding spots, reduce stress, and help maintain water quality.
  • Decorations: Include decorations like rocks, driftwood, and caves to create a diverse environment. Ensure there are no sharp edges that could injure the fish.


  • Lighting: Provide moderate lighting to support plant growth and mimic natural daylight cycles. Use a timer to maintain a consistent day/night cycle, typically around 8-10 hours of light per day.

Cycling the Tank

  • Cycle the Tank: Before adding guppies, cycle the tank to establish beneficial bacteria. This process, which can take several weeks, involves setting up the tank, running the filter, and gradually building up beneficial bacteria levels to convert harmful ammonia and nitrites into less harmful nitrates.

Adding Guppies

  • Stocking Density: In a 20 gallon guppy tank (80 liters), you should be able to keep 10-12 guppies. This of course depends on the number of tank mates, and also how many guppy babies they produce. So take this into account.
  • Acclimation: Acclimate the guppies to the tank water gradually to prevent shock. This usually involves floating the bag they came in on the tank water, then slowly adding small amounts of tank water to the bag over the next 15-30 minutes before releasing them into the tank.


  • Regular Maintenance: Perform regular water changes, typically 10-20% weekly, to maintain water quality.

By following these steps, you’ll create a thriving environment for your guppies, ensuring they remain healthy, vibrant, and active. Remember, the key to a successful aquarium lies in consistent maintenance and care.

20 Gallon Guppy Tank (80 Liters) – How To Set It Up - "Male Guppy" by Mihnea Stanciu is licensed under CC BY 2.0.
20 Gallon Guppy Tank (80 Liters) – How To Set It Up – “Male Guppy” by Mihnea Stanciu is licensed under CC BY 2.0.

Tank Mate Considerations

When selecting tank mates for guppies, it’s crucial to consider several factors to ensure a harmonious and stress-free environment for all inhabitants. Guppies are peaceful and sociable fish, but not all species will coexist peacefully with them. Here are important considerations for choosing compatible tank mates for guppies:


  • Avoid Aggressive Fish: Steer clear of aggressive or fin-nipping species that might harass or injure guppies. For instance, larger cichlids, bettas, and some barbs can be aggressive towards guppies.
  • Choose Peaceful Companions: Opt for fish with a peaceful nature that are known to coexist well in community tanks.
  • Similar Size: Select tank mates that are roughly the same size as guppies to prevent predation. Larger fish might see guppies, especially fry, as food.
  • Compatibility: Ensure the chosen species have similar water and environmental requirements (temperature, pH, hardness) as guppies. This ensures all the fish thrive under the same conditions.
  • Complementary Activity Levels: Choose fish that have similar activity levels to guppies to avoid overwhelming them. Guppies are active but not overly boisterous.
  • Habitat Preferences: Consider fish that occupy different levels of the tank. Guppies often swim in the middle and upper parts of the aquarium, so species that prefer the bottom can be a good complement, ensuring they don’t compete for space.
  • Breeding Behavior: Some fish may prey on guppy fry, so if breeding guppies and raising the fry in the same tank is a goal, select tank mates less likely to eat the young fish.
  • Overpopulation: Be cautious with other livebearer species that might breed prolifically, as this could lead to overpopulation and resource competition.
  • Similar Dietary Needs: Ensure the dietary requirements of the tank mates are compatible with those of guppies to simplify feeding and ensure all fish get the nutrition they need.

Suitable Tank Mates for Guppies

Here are some examples of fish that are often compatible with guppies:

  • Tetras: Many tetra species are peaceful and share similar water condition requirements.
  • Corydoras Catfish: These bottom dwellers are peaceful and can help keep the substrate clean.
  • Mollies and Platies: Like guppies, they are livebearers and generally peaceful, although care should be taken to manage population growth.
  • Dwarf Gouramis: They are generally peaceful and can coexist with guppies if the tank is spacious enough to provide everyone with their own territory.
  • Harlequin Rasboras: Known for their peaceful nature and beautiful coloration, they make great companions for guppies.
  • Shrimp and Snails: Many types of freshwater shrimp and snails are excellent choices for adding diversity without increasing the risk of aggression. They also help with algae control and clean-up.

Always research specific species before adding them to your tank to ensure compatibility. Introduce new fish gradually and monitor the tank closely for any signs of aggression or stress. Maintaining a well-balanced, peaceful community tank requires careful planning, but it can be incredibly rewarding to see a diverse group of species coexisting happily.


In conclusion, a 20 gallon guppy tank (80 liters) presents a wonderful opportunity to delve into the fascinating realm of aquarium hobbying. By carefully selecting compatible tank mates, maintaining optimal water conditions, and providing a varied and nutritious diet, you can create a thriving ecosystem that showcases the natural beauty and engaging behavior of guppies. Remember, the key to a successful guppy tank lies in understanding the specific needs of your aquatic inhabitants and committing to regular maintenance routines. With patience and attention to detail, your 20 gallon guppy tank (80 liters) will become a vibrant centerpiece, bringing a slice of aquatic life into your home.