Large Freshwater Aquarium Fish (Species Guide): The Complete Guide

Large freshwater aquarium fish can be stunning and impressive species with their vibrant colors and interesting behaviors. In this species guide, we will explore some of the most popular and fascinating options for your freshwater aquarium setup.

From the massive arapaima to the stunning flowerhorn cichlid, we will discuss the sizes, habitats, and care requirements of these amazing fish to help you make an informed decision on which species to choose. Whether you are a beginner or an experienced aquarist, there is a large freshwater fish for every level of expertise. So, let’s dive in and explore the world of large freshwater aquarium fish.

Factors To Consider When Choosing Large Freshwater Fish

Freshwater aquariums provide a relaxing atmosphere while being a beautiful centerpiece for any room. Choosing large freshwater fish can be challenging, and it’s crucial to consider several factors before making a final decision. Here are some key factors to keep in mind when selecting large freshwater fish.

Size Of Aquarium And What It Can Accommodate

Before making a decision, you need to consider the size of the aquarium and what it can accommodate. It is essential to choose a fish breed that suits the size of your aquarium, especially when selecting large freshwater fish. Some fish can grow up to a foot in length, and it’s crucial to ensure that your tank has enough water volume to support the fish.

  • 55-gallon aquarium – angelfish, bala shark, rainbow shark
  • 75-gallon aquarium – discus fish, oscar fish
  • 125-gallon aquarium – arowana, flowerhorn cichlid

Compatibility With Other Fish Species

It’s crucial to ensure that the large freshwater fish you select are compatible with other fish species in your aquarium. Avoid keeping aggressive fish species with peaceful fish species, as it can lead to injuries and even death of weaker fishes.

  • Gourami – peaceful towards other fish but aggressive towards their own species.
  • Angelfish – compatible with most fish breeds but can become territorial during breeding season.
  • Oscar fish – aggressive and territorial, can be kept in a group of three or more.

Water Conditions And Specific Dietary Needs

Water conditions are essential to keep your fish healthy and maintain their vibrant colors. Large freshwater fish require specific water conditions that need to be maintained regularly to prevent fish stress and illness. Additionally, it’s also crucial to provide a well-balanced diet that caters to specific dietary needs of the fish.

  • Discus fish – water temperature between 82-86°f and a ph range between 6. 0-7. 0. Diet includes high protein and a mix of flake and pellet food.
  • Arowana – prefer warmer water temperature around 80°f, and a ph range between 6. 5-7. 5. They require live protein foods such as insects, small crustaceans, and fish.
  • Bala shark – water temperature between 72-82°f and ph range between 6. 5-7. 5. They are omnivorous and require a balanced diet of pellets, flake food, and fresh vegetables.

Behavioral Traits And Maintenance Requirements

Large freshwater fish can have different behaviors and may require specific maintenance needs. Understanding the fish behavior can also help you create a safe and healthy environment. Some large freshwater fish may require frequent water changes, high-quality filtration, and adequate oxygen levels.

  • Flowerhorn cichlid – highly aggressive and territorial, requires frequent water changes and a powerful filtration system.
  • Angelfish – can be shy and need hiding places, requires a moderate filtration system, and weekly water changes.
  • Arowana – great jumpers, need tight-fitting lids, require a large tank, and pristine water conditions.

Choosing large freshwater fish can be an exciting and rewarding experience. It’s crucial to consider aquarium size, compatibility with other fish species, water conditions, specific dietary needs, and behavioral traits before choosing your large freshwater fish. Keeping these factors in mind can help you create a vibrant, healthy, and visually impressive aquarium.

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Commonly Available Large Freshwater Fish Species

Large Freshwater Aquarium Fish (Species Guide)

If you’re looking to add some size and intrigue to your freshwater aquarium, consider exploring some of the most commonly available large freshwater fish species. These fish require specific care, but when provided with the right environment, they can flourish and provide a stunning display.


  • Physical characteristics: long, sleek body, with a variety of color patterns (silver, gold, green, and others).
  • Behavior: active swimmers, with a tendency to jump out of the water.
  • Compatibility: best kept with other large fish that won’t fit in their mouths, such as angelfish or silver dollars.
  • Maintaining their health: arowanas are carnivorous and require a varied diet consisting of live or frozen foods. Keep the tank clean and provide plenty of swimming space.


  • Physical characteristics: silver, black, or red colors with a distinctive diamond shape.
  • Feeding habits: omnivores that enjoy a mix of plant matter and protein. They are known to take bites out of other fish in the tank if not provided with enough food.
  • Compatibility: require a large tank due to their size and can be somewhat aggressive towards smaller fish.
  • Maintaining their health: provide plenty of hiding spaces and plants in the tank as they enjoy densely planted environments. Maintain good water quality.


  • Physical characteristics: dark, bold colors with a distinctive razor-sharp dorsal fin.
  • Feeding habits: they are carnivorous and enjoy a mix of live and frozen foods.
  • Tank size: oscars require a large aquarium with excellent filtration systems.
  • Maintaining their health: oscars require clean, well-oxygenated water and a well-balanced diet. These fish can be quite aggressive towards other fish, so carefully choose tank mates.

Discus Fish:

  • Physical characteristics: oval-shaped body with a bright color pattern.
  • Feeding habits: they are omnivores and require a varied diet of live and frozen foods.
  • Compatibility: discus are generally peaceful and can be kept with other peaceful species.
  • Maintaining their health: discus require a clean, well-oxygenated tank with a carefully controlled ph level to thrive.


  • Physical characteristics: distinctive, armored body and a wide variety of colors and patterns.
  • Feeding habits: they are primarily herbivores and need a varied diet of vegetables and algae wafers.
  • Compatibility: can be kept with other peaceful species, but require plenty of hiding spots as they are nocturnal.
  • Maintaining their health: provide a well-filtered tank with a variety of hiding spots and plant matter. They may require additional feeding in a community tank.

Adding large freshwater fish species to your aquarium can be a rewarding experience, but it requires dedicated care and attention. By carefully choosing tank mates and maintaining good water quality, you can provide your fish with a healthy, happy life.

Care And Maintenance Of Large Freshwater Fish Species

Large freshwater fish species provide an exciting addition to any aquarium. However, caring for these magnificent creatures comes with some challenges. To ensure your fish live long and healthy lives, it is essential to practice proper care and maintenance techniques.

In this section of the species guide, we will take a closer look at the best practices for keeping your large freshwater fish healthy and happy.

Tips For Optimal Care And Maintenance Of Large Freshwater Fish, Including Tank Preparation, Feeding, And Disease Prevention

Taking care of large freshwater fish species can come with a steep learning curve.

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  • Tank preparation: large freshwater fish require a great deal of space to live in comfortably. Always ensure that the aquarium is appropriately sized, well-filtered, and well-oxygenated.
  • Feeding: nutritious and balanced diets are crucial for these fish. Ensure that you feed them an appropriate amount and type of food according to their species.
  • Disease prevention: maintaining a clean and tidy tank, regular water changes, and providing suitable living conditions can help prevent diseases.

Best Practices For Keeping The Tank Environment Stable And Healthy

Keeping a stable and healthy environment for your fish is essential for their longevity.

  • Regularly clean the tank to remove any uneaten food, waste, and debris.
  • Always monitor and maintain the water parameters within suitable levels for the species.
  • Avoid overstocking the aquarium with too many fish to prevent overcrowding and water contamination.

Troubleshooting Common Health And Behavioral Issues

Despite your best efforts, sometimes your fish can develop health or behavioral issues.

  • Loss of appetite: check water quality, aquarium conditions, and food suitability.
  • Aggressive behavior: ensure the tank is large enough, and its inhabitants are compatible.
  • Signs of disease: immediate action is required, including isolating the affected fish and seeking professional advice.

By following these essential tips, practices, and troubleshooting guidelines, you can provide your large freshwater fish with a suitable, safe, and healthy home.

How Does the Nitrogen Cycle Impact Large Freshwater Aquarium Fish?

The nitrogen cycle in aquariums explained: In a large freshwater aquarium, the nitrogen cycle plays a crucial role in maintaining fish health. This cycle begins with fish waste, which produces ammonia. Beneficial bacteria then convert ammonia into nitrite, and subsequently into less harmful nitrate. Regular water testing and proper filtration ensure that the nitrogen cycle remains balanced, preventing toxic build-up and creating a healthy habitat for aquarium fish.

Frequently Asked Questions Of Large Freshwater Aquarium Fish (Species Guide)

What Is The Minimum Tank Size For Large Freshwater Aquarium Fish?

Large freshwater fish require at least a 75-gallon tank to give them ample swimming space.

Which Fish Species Are Suitable For A Community Tank?

Community tank suitable large freshwater fish species include angelfish, discus fish, and rainbowfish.

Can Large Freshwater Fish Survive With Artificial Plants?

Yes, they can. However, they prefer natural plants as it offers them shelter, food, and improved water quality.

Do Large Freshwater Fish Require Special Filtration?

Yes. Large freshwater fish produce a lot of waste, so it’s best to use a filter that can handle their waste production.

Can Large Freshwater Fish Thrive In Brackish Water?

Some large freshwater fish species can tolerate slightly salty water, but it’s best to research their specific requirements beforehand.


To sum up, freshwater aquarium fish are fascinating creatures that can make great additions to any aquarium. Whether you prefer the colorful and playful koi or the calm and regal angel fish, there is sure to be a species that sparks your interest.

Remember to keep in mind their unique needs and characteristics when choosing which fish to add to your tank. With proper care and attention, these fish can provide years of enjoyment for their owners. Additionally, it is important to research and understand the impact of introducing non-native species to your local ecosystems.

By following these tips and guidelines, you can create a beautiful and thriving freshwater aquarium that is both enjoyable to watch and environmentally responsible. So go ahead and explore the world of freshwater aquarium fish – the possibilities are endless!

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