Koi Angelfish

Koi Angelfish are alluring freshwater fish related to the well-known Common Angelfish. With their distinctive, diverse color patterns and majestic presence, they have captured the hearts of aquarium enthusiasts. These amiable fish demand moderate care, making them a superb option for community aquariums.

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Care DIfficulty


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South America

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6 inches (15 cm)

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10 years

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Table of contents

Origin, Appearance, Size, and Lifespan

The Koi Angelfish, or Pterophyllum scalare, is a cherished freshwater fish originating from the Amazon River basin in South America. You'll commonly encounter them in the slow-moving tributaries and backwaters throughout Brazil, Colombia, and Peru.

In their natural habitat, Koi Angelfish are frequently found in calm, deep waters with ample vegetation. These plants provide both shelter and food, while the dark riverbeds accentuate their vibrant colors. These social fish flourish in groups of at least five, but it's not rare to spot them in schools of 10 to 15 or more.

Their natural environment consists of warm, soft, and slightly acidic water. The temperature usually ranges from 75 to 82 degrees Fahrenheit (24 to 28 degrees Celsius), with a pH level of 6.0 to 7.5, and water hardness between 3 to 8 dGH. To replicate a similar environment in your aquarium, ensure a stable water temperature, employ a high-quality filtration system, and include live plants and driftwood.

By closely replicating the Koi Angelfish's natural habitat and maintaining the correct water conditions, you'll be laying the foundation for a healthy and content life for your fish in your aquarium.

Koi Angelfish are admired for their unique marbled patterns, which typically include a blend of white, orange, and black colors, resembling Japanese Koi. These striking hues make them a captivating and visually appealing addition to aquariums. Although they can grow to be quite large, reaching up to approximately 6 inches (15 cm) in body size, their elegant fins and tranquil demeanor make them an ideal selection for those seeking a serene, visually stunning aquatic display. These elegant fish delight onlookers as they gracefully navigate the tank, earning them a beloved status among hobbyists of various skill levels.

With attentive care, Koi Angelfish can have a lifespan of up to 10 years. As social creatures, they thrive in groups and are best kept in schools of at least five individuals. To encourage their well-being and ensure a lengthy life in captivity, it's crucial to provide a densely planted aquarium with numerous hiding spots, as well as a diverse diet consisting of high-quality flakes, pellets, and frozen foods.

Fun Facts

Now that we have learned more about the appearance and lifespan of Koi Angelfish, in this section, we'll spotlight some captivating facts about these elegant fish that make them stand out in the aquarium hobby. From their remarkable coloration to their peaceful behavior, Koi Angelfish are full of surprises and are certain to charm any aquarist.

  • Distinctive Koi pattern: Koi Angelfish display a unique marbled coloration that resembles the highly valued Japanese Koi carp. This stunning color pattern makes them an eye-catching addition to any aquarium.
  • Variety of color patterns: Koi Angelfish come in a wide range of color patterns, with some fish featuring more white, while others have a dominance of orange or black. This variation ensures that each Koi Angelfish is unique, adding to their appeal in a community aquarium.
  • Cichlid family member: Despite their peaceful nature, Koi Angelfish are members of the Cichlid family. However, they are one of the more docile species within the family, making them suitable for community tanks.
  • Intelligent fish: Koi Angelfish are known for their intelligence and can recognize their owners, often swimming to the front of the tank when they approach. This interactive behavior adds to their charm and makes them a favorite among aquarists.
  • Spawning behavior: Koi Angelfish form monogamous pairs during breeding and share the responsibility of caring for their eggs and fry. This cooperative behavior showcases their nurturing side and offers aquarists a unique opportunity to observe their fascinating spawning process.

Now that you've uncovered some intriguing facts about Koi Angelfish, you'll be better prepared to appreciate their beauty and intricacies in your aquarium. In the following section, we'll provide recommendations on tank setups, ensuring your Koi Angelfish have an ideal environment to thrive and showcase their graceful features.

Recommended Tank Setups

Each setup includes the core components—tank, filter, heater, lighting, substrate, and more—ensuring that you can create an appropriate environment for Koi Angelfish and other compatible freshwater fish species in your aquarium. As you move from budget-friendly to high-end setups, you will also have more options for customization, aesthetics, and advanced features. Koi Angelfish can grow quite large, so it is essential to have a spacious tank to accommodate their needs. Typically, Koi Angelfish are priced between $5 and $20 per fish, although prices can vary based on factors such as size, quality, and availability.

Budget-friendly setup (around $200):

  • Tank: 29-gallon aquarium with a hood or glass canopy ($40 - $70)
  • Filter: Hang-on-back (HOB) or sponge filter rated for 29 gallons ($20 - $40)
  • Heater: 100-150 watt adjustable aquarium heater ($15 - $30)
  • Lighting: Basic LED aquarium light ($20 - $50)
  • Substrate: Inexpensive aquarium sand or small gravel ($10 - $20)
  • Decor: A few pieces of driftwood and rocks, along with low-cost live plants like Java Fern and Anubias ($20 - $40)
  • Fish: 2 to 4 Koi Angelfish, depending on their size ($10 - $80)
  • Thermometer: $3 - $10
  • Substrate Vacuum: $10 - $25
  • Fish Net: $2 - $10
  • Algae Scraper or Magnetic Cleaner: $5 - $20
  • Siphon and Bucket: $15 - $30
  • Test Kit: $15 - $50
  • Fish Food: $5 - $20
  • Water Conditioner: $5 - $15

Mid-range setup (around $400 - $650):

  • Tank: 55-gallon aquarium with a hood or glass canopy ($100 - $200)
  • Filter: Canister filter or high-quality HOB filter rated for the tank size ($60 - $150)
  • Heater: 200-300 watt adjustable aquarium heater ($25 - $50)
  • Lighting: LED aquarium light with adjustable settings for plant growth and color enhancement ($50 - $150)
  • Substrate: Nutrient-rich aquarium substrate designed for planted tanks ($20 - $40)
  • Decor: A mix of driftwood, rocks, and live plants such as Amazon Swords, Java Fern, Anubias, and Cryptocoryne species ($40 - $80)
  • Fish: 4 to 6 Koi Angelfish, depending on their size ($20 - $120)
  • Thermometer: $3 - $10
  • Substrate Vacuum: $10 - $25
  • Fish Net: $2 - $10
  • Algae Scraper or Magnetic Cleaner: $5 - $20
  • Siphon and Bucket: $15 - $30
  • Test Kit: $15 - $50
  • Fish Food: $5 - $20
  • Water Conditioner: $5 - $15

High-end setup (above $800):

  • Tank: 75-gallon rimless aquarium with a glass canopy ($200 - $400)
  • Filter: High-quality canister filter rated for the tank size ($100 - $250)
  • Heater: 300-400 watt adjustable aquarium heater with an external temperature controller ($40 - $80)
  • Lighting: Advanced LED lighting system with customizable settings for plant growth, color enhancement, and day/night cycles ($150 - $300)
  • Substrate: Premium aquarium substrate designed for planted tanks, with added root tabs for extra plant nutrition ($30 - $60)
  • Decor: A combination of driftwood, rocks, and live plants to create a natural aquascape, featuring plant species such as Amazon Swords, Java Fern, Anubias, Cryptocoryne species, and carpeting plants like Dwarf Hairgrass or Monte Carlo ($60 - $150)
  • Fish: 6 to 8 Koi Angelfish, depending on their size ($30 - $160)
  • Thermometer: $3 - $10
  • Substrate Vacuum: $10 - $25
  • Fish Net: $2 - $10
  • Algae Scraper or Magnetic Cleaner: $5 - $20
  • Siphon and Bucket: $15 - $30
  • Test Kit: $15 - $50
  • Fish Food: $5 - $20
  • Water Conditioner: $5 - $15

Please note that these numbers are just recommendations, and you should consider other factors such as tank mates and individual fish personalities when deciding how many Koi Angelfish to keep in your aquarium. Prices may vary depending on location, brand, and availability.

Set Up Your Tank

In the previous section, we discussed the recommended tank setups for your Koi Angelfish and other fish. Now that you have a better understanding of what's required, let's dive into the step-by-step process of setting up your aquarium. These steps will guide you through selecting the ideal location for your tank, cleaning and preparing the tank, installing essential equipment, and cycling the water to create a healthy environment for your fish. We'll also cover the proper acclimation process to ensure a smooth transition for your Koi Angelfish and other fish into their new home. By following these guidelines, you'll be well on your way to creating a thriving aquatic ecosystem for your fish to flourish in.

  • Step #1: Choose the perfect spot for your aquarium, making sure it's away from direct sunlight, heat sources, and drafts. Ensure the surface is level and sturdy enough to support your filled tank. If your aquarium requires a stand, assemble it according to the manufacturer's instructions and place the empty tank on it.
  • Step #2: Next, clean the tank by rinsing it with clean water (avoid using soap or chemicals) to remove dust or debris. Wipe the inside with a clean cloth or paper towel. Rinse the substrate (sand or gravel) thoroughly in a bucket until the water runs clear, then spread it evenly across the bottom of the tank, creating a slight slope towards the back for visual depth.
  • Step #3: Before filling the tank with water, plan the layout of your aquarium, including the position of equipment like heaters and filters. This will make it easier to set up and maintain the tank in the long run. Install the heater and filter according to the manufacturer's instructions. If you're using a sponge or under-gravel filter, place it beneath the substrate before adding water.
  • Step #4: Decorate the tank with driftwood, rocks, and plants to create hiding spots and a visually appealing environment, ensuring there are open swimming areas for your fish. When decorating the tank, be careful to arrange driftwood, rocks, and plants in a way that won't damage or obstruct the equipment. You can also anchor plants to driftwood or rocks to help them stay in place.
  • Step #5: Fill the tank with water treated with a water conditioner if your tap water contains chlorine or chloramines. Place a clean plate or plastic bag on the substrate to prevent disturbance while filling. Fill the tank until it's about 2/3 full. Attach the aquarium light to the hood or canopy, following the manufacturer's instructions. Consider using a timer for your aquarium light to maintain a consistent day and night cycle, which is essential for fish and plants. Connect the heater, filter, and any additional equipment (air pump, CO2 system) to power sources, and install the thermometer in an easily visible location.
  • Step #6: Top off the water, leaving space between the water surface and the top of the tank for oxygen exchange. Turn on the filter, heater, and other equipment. Monitor the water temperature and adjust the heater as needed. Allow the tank to cycle for 4-6 weeks to establish beneficial bacteria and stabilize water parameters. During the cycling process, you can add a bacterial starter culture to speed up the establishment of beneficial bacteria in the tank. Use an aquarium test kit to monitor ammonia, nitrite, and nitrate levels.
  • Step #7: After the tank has cycled and water parameters are stable, slowly acclimate your Koi Angelfish and other fish to the tank's conditions before introducing them. Begin by floating the unopened fish bag in the tank for 15-20 minutes to equalize the temperature. Afterward, open the bag and add a small amount of tank water to it. Continue adding small amounts of tank water to the bag every 5-10 minutes for at least 30-60 minutes, allowing the fish to adjust to the new water chemistry gradually. Use a net to gently transfer the fish from the bag to the tank, avoiding any unnecessary stress or exposure to the water from the bag.
  • Step #8: Once all the fish are introduced, establish a consistent daily feeding schedule, providing high-quality food in appropriate amounts for your fish species. Perform regular water changes (20-30% every 1-2 weeks) and monitor water parameters using a test kit to maintain a healthy environment for your fish. Observe your fish closely for any signs of stress or illness, especially during the first few weeks after introduction. Be prepared to take action if necessary, such as adjusting water parameters or seeking advice from an experienced aquarist.

By following this step-by-step guide and incorporating the additional setup tips, you can create a thriving aquatic environment that will help your Koi Angelfish and other fish flourish in their new home.

Recommended Water Parameters

To keep your Koi Angelfish healthy and happy, it's important to maintain specific water parameters in your aquarium. Here's a breakdown of what to aim for:

  • Temperature: Keep the water between 75°F and 82°F (24°C and 28°C) for optimal comfort.
  • pH: Aim for a slightly acidic to neutral pH of 6.0 to 7.5, but they can tolerate slight fluctuations.
  • Hardness: Soft to moderately hard water (3-12 dGH) is ideal, though they can adapt to slightly harder water.
  • Ammonia, Nitrite, and Nitrate: Keep ammonia and nitrite at 0 ppm, and maintain nitrate levels below 20 ppm.
  • Lighting: Provide moderate lighting with shaded areas and plants to prevent stress.
  • Water movement: Moderate water flow is best, mimicking their natural slow-moving habitat.

Make sure to test your aquarium water regularly and perform necessary water changes to keep the environment stable.

Routine Water Maintenance

Water changes are crucial for a healthy Koi Angelfish tank. They help remove excess nutrients, waste, and toxins. Here's a suggested routine:

  • Weekly water changes: Replace 20-25% of the tank water every week.
  • Test water parameters: Check pH, ammonia, nitrite, nitrate, and hardness regularly.
  • Use a gravel vacuum: Clean the substrate during water changes.
  • Dechlorinate the water: Treat tap water with a water conditioner before adding it to the aquarium.
  • Match temperature and pH: Ensure new water is similar to the tank water.
  • Acclimate the fish: Give your fish time to adjust to new conditions after water changes.

In addition to routine water maintenance, consider the following to ensure the health of your fish and the overall appearance of your aquarium:

  • Monitor lighting duration: Keep track of how long your aquarium lights are on each day, aiming for a consistent 8-10 hour photoperiod. Too much light can lead to excessive algae growth.
  • Plant maintenance: Regularly trim live plants to maintain their health and appearance. Remove any dead leaves or plant matter to prevent water quality issues.
  • Filter maintenance: Clean or replace the filter media as recommended by the manufacturer, usually every 4-6 weeks. Avoid replacing all filter media at once, as this can disrupt the beneficial bacteria and lead to water quality issues.

Diet and Feeding Schedule

Koi Angelfish are omnivores and require a diverse diet. Here are some feeding guidelines:

  • Flakes and pellets: Use high-quality flake or pellet food designed for angelfish.
  • Frozen and live foods: Offer brine shrimp, bloodworms, daphnia, or mosquito larvae as occasional treats.
  • Vegetable matter: Provide blanched spinach, zucchini, or cucumber for added nutrients.
  • Feeding frequency: Feed modest portions two to three times a day, and avoid overfeeding.

Stress and Diseases

Koi Angelfish may experience stress from various sources, such as poor water quality, aggression, or unsuitable tank conditions. Identifying and addressing these stressors is vital for your fish's health and well-being:

  • Watch for stress signs: Keep an eye on your Koi Angelfish for unusual behavior like hiding, lethargy, color loss, or rapid breathing, which may indicate stress.
  • Check water quality: Test your aquarium water to ensure it meets the ideal parameters and conduct regular water changes to maintain a healthy environment.
  • Monitor tank mates: Make sure your Koi Angelfish aren't being harassed or attacked by other fish and remove any aggressive tank mates if needed.
  • Create a suitable habitat: Provide plenty of hiding spots, appropriate lighting, and a properly sized tank for your fish.

While Koi Angelfish are generally hardy, they can be susceptible to some common fish diseases, such as:

  • Ich (white spot disease): A prevalent parasitic infection causing white spots on the body and fins, lethargy, and appetite loss. Treat Ich with aquarium salt or anti-parasitic medication and raise the water temperature to around 82°F (28°C).
  • Fin rot: A bacterial infection that leads to frayed or discolored fins and tail. Treat fin rot with a partial water change, aquarium salt, and antibacterial medication containing erythromycin or tetracycline.
  • Velvet disease: A parasitic infection causing a yellow or brownish velvet-like coating on the fish's body. Treat velvet disease with anti-parasitic medication containing copper sulfate or formalin.
  • Swim bladder disease: A condition where fish have difficulty swimming upright. Treat swim bladder disease by fasting the fish and offering them blanched peas, and consider using an antibacterial medication if needed.

Prevent diseases in Koi Angelfish by maintaining excellent water quality, avoiding overfeeding, and providing a balanced diet. Quarantine new fish before adding them to the main tank and promptly address any signs of illness.


Breeding Koi Angelfish can be a challenging undertaking, but it is achievable with the right setup and conditions. Follow these steps to breed Koi Angelfish:

  • Step #1: Create a suitable breeding environment with a separate 20-gallon or larger breeding tank, a pH level of around 6.5 to 7.0, and a temperature of about 80°F (27°C). Maintain soft water (3-12 dGH) and include hiding spots like plants and spawning sites, such as vertical slates or broad leaves for the fish's comfort.
  • Step #2: Select healthy, mature male and female Koi Angelfish for breeding. Males have a more angular body and a nuchal hump, while females are rounder with a smaller hump. You can also observe their breeding tube to determine the gender.
  • Step #3: Prepare the breeding pair with a high-protein diet of live or frozen foods for several weeks to help them build strength and energy.
  • Step #4: Encourage spawning by introducing the pair to the breeding tank and maintaining optimal water conditions. Koi Angelfish usually lay their eggs on the spawning sites like vertical slates or broad leaves.
  • Step #5: Care for the eggs and fry by removing the breeding pair after spawning. Eggs will hatch within 48-72 hours, and the fry will become free-swimming after several days. Feed them freshly hatched brine shrimp or other suitable fry food.
  • Step #6: Monitor the growth and development of the fry, and separate them by size if needed to prevent larger fry from preying on smaller ones.

Breeding Koi Angelfish can be a rewarding experience for experienced hobbyists. Patience and the right conditions are key to success.

Recommended Tank Mates

Here are the top 10 recommended tank mates for Koi Angelfish:

  1. Dwarf Gouramis
  2. Rummy Nose Tetras
  3. Corydoras Catfish
  4. Mollies
  5. Platies
  6. Zebra Loaches
  7. Ghost Shrimp
  8. Nerite Snails
  9. Harlequin Rasboras
  10. Otocinclus Catfish

Remember to avoid large, aggressive fish like cichlids, and predatory species, as they may harm or eat the Koi Angelfish. Always observe the behavior of new fish and ensure they don't cause stress or aggression towards the Koi Angelfish.


In summary, Koi Angelfish are a captivating species of freshwater fish renowned for their striking colors and hardiness. These fish necessitate specific water parameters, a well-balanced diet, and a suitable environment to thrive in captivity. However, with the right conditions, they can live for several years and be an excellent addition to any aquarium. When selecting tank mates, it's crucial to choose peaceful and non-aggressive species to ensure a harmonious community. Breeding Koi Angelfish can be a challenging but rewarding experience for experienced hobbyists, and patience and ideal conditions are key to success. Overall, Koi Angelfish are a stunning and lively species that can enhance any aquatic display with their vibrant hues and lively behavior.

Frequently Asked Questions

What is the ideal tank size for Koi Angelfish?

When setting up a home for Koi Angelfish, a 30-gallon tank is the minimum recommended size for a small group. Opting for a larger tank is even better, as it helps keep water conditions stable while offering plenty of room for your fish to swim.

How many Koi Angelfish should be kept together?

Koi Angelfish are social fish and thrive in groups of at least 4-6 individuals. Keeping a larger group will help your fish feel safer and encourage them to display their fascinating natural behaviors.

What water parameters do Koi Angelfish require?

Koi Angelfish thrive in water temperatures between 76°F and 82°F (24°C and 28°C), a pH between 6.5 and 7.0, and soft to moderately hard water with a hardness between 3 and 12 dGH.

What do Koi Angelfish eat?

Koi Angelfish are omnivorous and require a varied diet. Feed them a mix of high-quality flake or pellet food, along with live or frozen foods such as brine shrimp, bloodworms, and daphnia.

Are Koi Angelfish compatible with other fish?

Yes, Koi Angelfish are generally peaceful and can coexist with other similarly sized, non-aggressive fish species. Ideal tank mates include small tetras, rasboras, corydoras catfish, and small plecos.

How can I differentiate between Koi Angelfish and other angelfish varieties?

Koi Angelfish have a distinct color pattern that includes a mix of orange, white, and black, resembling the coloration of koi fish. Other angelfish varieties have different color patterns and combinations.

How long do Koi Angelfish live?

With proper care and optimal tank conditions, Koi Angelfish can live for 8 to 10 years.

How do I breed Koi Angelfish?

Breeding Koi Angelfish can be challenging, as they require specific water conditions and a dedicated breeding tank. Prepare a separate breeding tank, and separate males and females before introducing them for spawning. Provide a suitable vertical surface, such as a slate or broad-leafed plant, for the angelfish to lay their eggs on.

Do Koi Angelfish require a planted tank?

While not strictly necessary, a planted tank is highly recommended for Koi Angelfish. Live plants provide hiding spots, improve water quality, and create a more natural environment that closely resembles their native habitat.

Can Koi Angelfish change color?

Yes, Koi Angelfish can undergo color changes as a result of several factors, such as stress, illness, or alterations in water conditions. If you observe your Koi Angelfish experiencing a loss of color, it's important to examine the water parameters and keep a close watch on their health.