Koi Angelfish Care Guide: The Freshwater "Koi"

By AFT Editorial • Last Update: September 27, 2025

Named for its striking resemblance to the famous Japanese Koi carp, the Koi Angelfish (Pterophyllum scalare) is a selectively bred marvel of the aquarium hobby. With its unique tri-color pattern of orange, black, and white, this fish brings a splash of vibrant color and the same elegance as its standard angelfish cousins. Despite its exotic looks, the Koi Angelfish is quite hardy and an excellent choice for aquarists who are ready to maintain a stable environment for this freshwater gem.

The Koi Angelfish is named for its beautiful tri-color pattern, not any relation to actual Koi carp.

This complete guide provides a comprehensive look into Koi Angelfish care, from understanding its unique, selectively bred genetics to mastering its daily needs. On this page, we cover the essential requirements for a proper tank setup, with a special focus on the need for a tall aquarium and stable water parameters. You'll discover the best diet and specific color-enhancing foods to make their orange and red hues truly vibrant. We also offer a detailed analysis of their semi-aggressive temperament, a crucial list of suitable tank mates, and practical advice on breeding this stunning freshwater fish.

Quick Facts

Koi Angelfish Fact Sheet
Topic	Details
Scientific Name	Pterophyllum scalare (Var. Koi)
Common Names	Koi Angelfish, Red Cap Angelfish
Care Level	Beginner to Intermediate
Temperament	Semi-aggressive
Adult Size	Up to 6 inches (15 cm) long and 8 inches (20 cm) or more in height
Minimum Tank Size	30 gallons (114 liters) for a pair; 55+ gallons for a community
Tank Shape	A tall tank is non-negotiable for their vertical body shape
Water Parameters	Temp: 76-82°F (24-28°C); pH: 6.0-7.5; Hardness: 3-10 dGH
Diet	Omnivore; requires a varied diet with color-enhancing foods
Lifespan	10-15 years in a well-maintained environment
Origin	Domesticated color morph; wild ancestors from South America

What Is a Koi Angelfish?

Despite the name, the Koi Angelfish is not a hybrid of a koi carp and an angelfish. They are 100% freshwater angelfish (Pterophyllum scalare). The “Koi” name comes purely from their tri-color pattern of orange/red, black, and white, which was developed by aquarists through careful selective breeding. Breeders isolated specific genes for these colors to create a fish that mimics the aesthetic of a traditional pond koi.

Appearance & Coloration

The appearance of the Koi Angelfish is its main draw. The goal of breeders is to achieve a fish with a clean white body, distinct black marbling, and a vibrant orange or red “cap” on its head.

Pattern Variability: No two Koi Angelfish are identical. Some may have extensive black marbling, while others are mostly white with just a few black spots. The amount and intensity of the orange also vary greatly.
Color Intensity: The vibrancy of the orange/red coloration is a strong indicator of the fish’s health, mood, and diet. Colors may fade when the fish is stressed, sick, or kept in poor water conditions. Conversely, their colors will intensify when they are healthy, well-fed, and especially during breeding.
Veiltail Variation: Like other angelfish varieties, the Koi Veil Angelfish exists and features the same coloration but with much longer, more dramatic flowing fins.

Temperament & Behavior

As members of the cichlid family, Koi Angelfish are considered semi-aggressive. Their behavior is identical to that of other common angelfish varieties. They are generally peaceful but will establish a social hierarchy and can become territorial, especially as they mature and form breeding pairs. They are predatory towards very small fish and invertebrates.

Tank Requirements & Habitat

Tank Size and Shape

Height is more important than length. A 30-gallon tall aquarium is a good starting point for a pair, but a 55-gallon tank or larger is highly recommended for a small group or a community setup. The height allows them to swim comfortably without their long fins dragging on the substrate.

Aquascape and Decor

Create a secure environment with vertical elements.

Plants: Tall plants like Amazon Swords and Vallisneria provide excellent cover.
Driftwood: Vertical or branching driftwood mimics their natural habitat and gives them places to hide and spawn.
Lighting: Quality lighting will support plant growth and enhance the fish’s colors. For the best vibrancy, we recommend an adjustable full-spectrum LED like the Fluval Plant 3.0, which allows you to fine-tune the color spectrum.

Water Parameters

Koi Angelfish need stable, clean water.

Temperature: 76-82°F (24-28°C). To ensure stability, a reliable heater is a must. The Cobalt Aquatics Neo-Therm Heater is an excellent, accurate choice.
pH Level: 6.0 to 7.5
Filtration: A gentle but effective filter is key. For a 55-gallon tank, a canister filter like the Fluval 307 provides great filtration without creating excessive current.

Diet and Feeding

A varied, omnivorous diet is crucial for health and color.

Staple Diet: Use a high-quality flake or pellet as the base.
Color Enhancement: This is especially important for Koi Angelfish. Feed foods rich in carotenoids like astaxanthin and beta-carotene to boost their red and orange colors. Hikari Cichlid Gold and New Life Spectrum Thera-A are excellent color-enhancing pellets.
Supplements: Offer frozen or live foods like brine shrimp, bloodworms, and daphnia several times a week.

Koi Angelfish Tank Mates

Choose tank mates carefully to avoid aggression and fin-nipping.

Good Tank Mates:

Tetras: Larger, peaceful tetras like Black Skirt, Rummy Nose, or Lemon Tetras.
Catfish: Corydoras, Bristlenose Plecos, and other peaceful bottom-dwellers.
Peaceful Barbs: Cherry Barbs or Odessa Barbs.
Gouramis: Pearl Gouramis are generally a good fit.

Tank Mates to Avoid:

Fin Nippers: Tiger Barbs are notorious for destroying angelfish fins.
Aggressive Cichlids: Avoid keeping them with African Cichlids, Oscars, etc.
Very Small Fish: Adult angels will eat Neon Tetras, guppy fry, and shrimp.

Breeding Koi Angelfish

The breeding process is the same as for other P. scalare varieties. A bonded pair will clean a vertical surface and lay their eggs, which they will then guard ferociously. A fascinating aspect of breeding Koi Angelfish is watching the color develop in the fry. They are often born pale and the characteristic orange and black patches will fill in as they grow over several weeks.

For a wider overview of care basics, see our Freshwater Angelfish pillar.

Frequently Asked Questions

Is a Koi Angelfish a hybrid of a koi and an angelfish?

No. It is a 100% freshwater angelfish (Pterophyllum scalare) that has been selectively bred to have a color pattern resembling a Koi carp.

Why is the orange color on my Koi Angelfish fading?

Color fading is most often caused by stress, poor water quality, or a lack of color-enhancing foods in their diet. Improve these factors, and their vibrancy should return.

What foods will make my Koi Angelfish's colors brighter?

Feed high-quality pellets that contain natural color enhancers like astaxanthin. Supplementing with krill, mysis shrimp, and daphnia will also help boost their red and orange pigments.

Are Koi Angelfish more difficult to care for than other angelfish?

No, their care requirements for tank size, water parameters, and temperament are identical to other common varieties like the Marble or Silver Angelfish.

How long do Koi Angelfish live?

With proper care in a well-maintained aquarium, a Koi Angelfish can live for 10 to 15 years.

Can I keep just one Koi Angelfish?

Yes, a single Koi Angelfish can be kept as a beautiful centerpiece fish. Keeping a single angelfish often results in less territorial aggression compared to keeping a breeding pair.

How do you tell a male from a female Koi Angelfish?

It is very difficult to sex them, especially when they are young. Mature males sometimes develop a small bump on their head (nuchal hump), but the only certain way is to observe their breeding tubes when spawning. The female's is short and blunt, while the male's is smaller and pointed.