How Many Discus Fish Can You Keep in a 40 Gallon Tank?

Aquarists face many challenges when setting up their dream tank, and choosing the perfect mix of fish for a 40-gallon tank is no easy feat. Among the popular species for hobbyists is the stunning, colorful discus fish, known for its unique shape and majestic appearance.

But, how many can you keep in a 40-gallon tank? Let’s dive into some important factors to consider when stocking your tank with discus fish, their requirements and compatibility with other fish, and some top tips to keep them happy and healthy.

It’s easier than ever to make mistakes when starting an aquarium, but understanding the basics of fishkeeping and discus fish care is all it takes to ensure a thriving, harmonious environment. In this guide, we’ll break down some key concepts and dispel common myths to give you the best shot at successfully maintaining a 40-gallon discus aquarium.

Get ready to embark on an exciting aquatic journey as we explore the incredible world of discus fish!

The Discus Fish: What You Need to Know

A Popular Choice

Discus fish, native to the Amazon River Basin, are a popular choice among aquarists due to their vivid colors, unique shape, and peaceful nature. They belong to the Cichlid family, but unlike some of their more aggressive relatives, discus are known for their peaceful and sociable temperament.

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Choosing the Right Tank Size

When selecting a tank for discus fish, it’s crucial to consider both size and water conditions. A 40-gallon tank is suitable, but always keep in mind that more space is better. In a 40-gallon tank, you can keep about 4-6 adult discus fish if you maintain excellent water quality and a suitable environment. However, if you can provide a larger tank, your discus fish will surely appreciate the extra swimming room and the chance to establish their territories.

Stocking Your 40-Gallon Discus Tank

Number of Discus Fish to Keep

As mentioned earlier, a 40-gallon tank can hold up to 4-6 adult discus fish. This number is based on the general rule of thumb that adult discus fish require at least 8-10 gallons per fish. The reason for this is that discus need space to swim and establish territories to avoid unwanted stress and aggression.

Compatibility with Other Fish

Discus fish are best kept with other peaceful, slow-swimming species that share similar water requirements. Some suitable tank mates include:

  • Neon tetras
  • Cardinal tetras
  • Rummy nose tetras
  • Corydoras catfish
  • Bristlenose plecos

When determining your optimal fish count, be sure to consider the bioload each species contributes to the tank.

Keeping Your Discus Fish Happy and Healthy

Water Parameters

Maintaining a stable environment is crucial for discus fish, as they are sensitive to fluctuations in water parameters. Here are the ideal water conditions for discus fish:

  • Temperature: 82-86°F
  • pH: 6.0-7.0
  • Hardness: Soft to moderately hard

Diet and Feeding

Feed your discus a balanced diet of high-quality pellets, flakes, and occasional treats like frozen or live brine shrimp, bloodworms, or white worms. Feed them several small meals a day, and closely monitor their appetite and behavior.

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Tank Maintenance

Regular tank maintenance is essential for your discus fish to thrive. Perform weekly water changes of 25-50% and monitor the water parameters closely to prevent any health issues. Invest in good filtration, and clean the filter media and tank regularly.

The Discus Fish and Aquarium Maintenance FAQ

  • How often should I feed my discus fish?
    • Feed your discus fish several small meals a day, watching their appetite and behavior closely.
  • What other fish can I keep with discus fish?
    • Some suitable tank mates for discus fish include neon tetras, cardinal tetras, rummy nose tetras, Corydoras catfish, and bristlenose plecos.
  • What water conditions do discus fish need?
    • Optimal water conditions for discus fish include a temperature of 82-86°F, pH of 6.0-7.0, and soft to moderately hard water hardness.
  • How many adult discus fish can I keep in a 40-gallon tank?
    • You can keep 4-6 adult discus fish in a 40-gallon tank, given that you maintain excellent water quality and a suitable environment.
  • What should I feed my discus fish?
    • Discus fish thrive on a balanced diet of high-quality pellets, flakes, and occasional treats like frozen or live brine shrimp, bloodworms, or white worms.


Keeping discus fish in a 40-gallon tank is possible, but it requires careful planning and diligent maintenance. With 4-6 discus fish, the right water conditions, and compatible tank mates, you can create a beautiful and peaceful underwater haven. Pay close attention to your fish’s behavior and overall health, and always be ready to make changes required to keep your discus fish happy and thriving. Happy fishkeeping!

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