Koi Angelfish Care Guide

Are koi angelfish good for beginners?

Koi Angelfish Care Guide7 mins read

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Tal Halperin
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Koi angelfish care guide

The koi angelfish, like other freshwater angelfish, is a variety of cichlid. However, unlike other cichlids, they have a unique flattened body shape that helps them hide amongst plants, rocks, and driftwood. In fact, the koi angelfish size and unique shape means they have some specific requirements.

Did you know, the koi angelfish is a captive-bred variety that has similar colors to the koi carp? It is not the same as the marine angelfish, which comes from a different species and needs different conditions – saltwater as opposed to freshwater. This article will look at the best conditions for freshwater angelfish like these, as well as go deeper into their care and the setup of a thriving angelfish tank.

Breed Overview

OriginAmazon and Orinoco river tributaries (Brazil and Venezuela)
Lifespan10-15 years
Size6-12” (15-30 cm)
ColourOrange, black, and white
FoodOmnivorous, but prefers protein
Tank SizeMinimum 55 gallons/208 liters
TemperamentSemi-aggressive, social, hierarchical
Water TypeFreshwater
Water Temperature78-84 F/23-28 C
Water pH5-7.5
Difficulty LevelIntermediate

Ideal Koi Angelfish Tank Setup

Like other freshwater angelfish, these fish prefer a tank that mimics their natural habitat in the Amazon and Orinoco river systems.

This means a heavily planted tank with lots of places to hide – but getting the right water parameters for these fish is also important. They are not a hardy species and can need quite specific conditions. Furthermore, koi angelfish size and shape means you may need a tank that is both tall and long.

Koi Angelfish Size, Parameters, And Tank Height

Koi angelfish size, parameters, and tank height
Keep this fish in social groups of 5 or 6, and add an extra 15 gallons (57 liters) per fish, as these fish are territorial.

You may hear that for angelfish you need at minimum a 30-gallon/114-liter tank. yet, to properly mimic their natural habitat, something much larger is always better.

With all freshwater fish, just because a fish is surviving, doesn’t mean that it’s thriving. Ideally, these fish need a minimum 55-gallon/208-liter tank. Keep them in social groups of 5 or 6, and add an extra 15 gallons (57 liters) per individual, as they can be territorial. Therefore, the more individual space they have, the less likely you will encounter aggression.

As they have a unique flattened shape and long trailing fins, angelfish need a tank that is tall enough to give them space to swim. Plus, some fish feel more comfortable at different levels of the water. Sometimes, koi angelfish size can be misleading; these fish grow taller than their length and can reach 8-10” in height (20-25 cm), so your tank height should ideally be double this.

Filter flow rate should be minimum 4x tank capacity, measured in gallons per hour. However, to maintain proper water quality, you should clean the tank once per week, changing 50% of the water.

Water Softness And Acidity

Water softness and acidity of koi angelfish tanks
In fact, softer water supports lower pH as is required by these fish.

All freshwater angelfish actually require slightly acidic water that is also relatively soft. This is because the natural habitats they come from in the Amazon are blackwaters – river systems that have high amounts of plant matter and carbon dissolved in them. The koi angelfish is no different, despite being captive bred.

How Can You Maintain These Conditions In Your Tank?

RO Water, short for reverse osmosis, is water that has some minerals removed from it. You can use it if you’re unsure of your water quality. Softer water supports lower pH as is required by these fish. Therefore if you have hard water but still want to keep this majestic species, this is a great option.

CO2 Injection If you’re lucky enough to have soft water anyway but want to ensure the pH is kept down to create the optimum environment for your angelfish, you can use this method. CO2 injectors are devices that can fit on the side of your tank near the filter and inject carbon dioxide into the water. This does so by causing the formation of carbonic acid.


Tankmates of koi angelfish tank
As angelfish, these guys do really well with other fish from their home, the Amazon Basin. Image from Flickr

As angelfish, these guys do really well with other fish from their home, the Amazon Basin. However, freshwater angelfish can actually get on with other fish too provided they share the need for soft acid water, which includes many species of tropical fish such as the following:

  • Ram cichlids
  • Swordtails
  • Platies
  • Mollies
  • Keyhole cichlids
  • Various types of tetras

They don’t enjoy being tankmates with fin-nipping fish as your angelfish will have beautiful trailing fins that can become tempting for fin-nippers. Likewise, some smaller fish are also not a good choice – especially if you keep them alone as opposed to in a shoal – as your angelfish might see them as prey.

Lastly, crustaceans such as snails or shrimps are not a good idea, as these would actually form part of your angelfishes’ diet in the wild.

Planting Your Tank

Planting your koi angelfish tank
Setting up a planted tank for your angelfish can be one of the most fulfilling parts of keeping these fish. Image from Flickr

Setting up a planted tank for your koi angelfish can be one of the most fulfilling parts of keeping these fish. Like with any aquarium, bear in mind that once planted, you won’t be able to rearrange your tank.

Although some other species can thrive without many plants or decorations, for angelfish, this is not optional. These river-dwelling fish need a planted environment that offers them options to hide in as well as help maintain water quality. This encourages their natural behavior, offers stimulation, and helps solve hierarchical disputes. Good plants include:

  • Amazon sword (females also love this as a place to hide their eggs)
  • Anubias
  • Java fern
  • Java moss
  • Amazon frogbit
  • Cabomba

Feeding Koi Angelfish

Feeding koi angelfish
The majority of their diet is composed of live invertebrates and sometimes even smaller fish that they find in their natural habitat. Image from Flickr

Due to their social nature and natural habitat, koi angelfish have particular feeding preferences. Read on to find out how these can influence feeding time – and what to know beforehand:

Diet Of Freshwater Angelfish In The Wild

Angelfish are omnivorous, but most of their diet in the wild involves live invertebrates and sometimes even smaller fish. Only a smaller amount is vegetables and plants!

It can be hard and expensive just to feed live foods. Therefore, like with all species a good quality pellet food is one of the best options. You can buy ones generically for tropical fish, or you can get ones that are specifically for angelfish and other cichlids.

Feeding, Tank Size, And Hierarchy

Angelfish are sensitive fish with complex social systems. As a result, tank environment and hierarchy struggles can affect feeding. Try to minimize competition as much as possible, as this can be a reason your angelfish is not eating.

When feeding freshwater angelfish, put some food at one end of the tank and some at the other. This means there isn’t too much competition and shyer fish can get enough food. It’s important to monitor all fish at feeding time and keep an eye out for strange behavior, as this can be a sign it is sick or dying.

Behavior And Temperament

Behavior and temperament in koi angelfish
The truth is that any fish behavior is going to be heavily affected by its environment.

The koi angelfish is sometimes called a non-aggressive fish, but sometimes called semi-aggressive. Therefore, if you’re new to this species, it may be hard to tell whether it’s right for you!

Any fish’s behavior depends heavily on the environment. Angelfish can be aggressive because they are territorial fish with a social hierarchy. However, if you give them the correct tank size, you can keep aggression to a minimum.

Social Hierarchy In Angelfish

All freshwater angelfish have a complex social hierarchy. As a result, it is best to keep them in groups of five to six.

You can spot dominant fish as they are the most active and eat the most food. However, you don’t have to worry about aggression yet. To an extent, angelfish can benefit from group dynamics. Scientific studies have shown that removing fish from their social groups makes them show a reduction in feeding and swimming. However, koi angelfish size can affect whether they get bullied, with smaller fish getting harrassed by larger ones. Therefore your tank should be large enough that there is not a risk of territorial dispute – with plenty of separate areas.

Pests And Diseases:

Pests and diseases in koi angelfish
The majority of parasitic infections can be treated by isolating your fish in a separate tank.

1. Parasitic Infections

Parasitic infections can be unpleasant for any fish. For freshwater angelfish, their unusual shape and long fins are sensitive spots that parasites can attack. Parasites range from ich to flukes, but all are generally caused by poor water quality.

You can treat most parasitic infections by isolating your fish in a separate tank. Then, use either aquarium salts or over-the-counter medication until they are parasite-free.

2. Fin Rot

Fin rot is important to spot in koi angelfish. Their long, flowing fins make them particularly vulnerable to poor water conditions.

To identify fin rot, look out for fins that are ragged and have unusual patches of color. These will often look sore and painful.  Fortunately, you can treat fin rot with over-the-counter antibacterial medication. However, it’s always best to isolate your fish first in a separate tank.

Breeding Koi Angelfish

Breeding koi angelfish
If you are wondering how angelfish mate, you may be surprised to know that these fish choose their own mates. Image from Flickr

Unlike some fish such as the goldfish that are peaceful in their mating habits, angelfish choose a mate based on dominance and submission. Often, it is the more aggressive males that get to mate with a certain female. Females also use dominance and submission to indicate their readiness to mate.

If you are wondering how angelfish mate, you may be surprised to know that these fish choose their own mates. Therefore, it’s best to encourage this natural process when breeding them. It’s best if you’ve already had both experience with breeding other aquarium fish before, as well as enough familiarity with angelfish behavior that you are able to spot changes that can indicate readiness to mate:

  • Fish spending all their time together
  • Female carrying eggs, with a more rounded abdomen
  • Fish locking lips
  • Fish following each other

Breeding In A Community Tank:

As you’ll most likely be choosing your breeding pair from within a community tank, it’s important to ensure surrounding fish don’t affect breeding. Here are a few important things to note:

  • Angelfish choose their own mates. Therefore, once your fish have reached sexual maturity (6-12 months) you can spot a breeding pair. Generally, this means fish that are spending all their time around each other. You can also see if a female is ready to spawn by observing if she is gravid (carrying eggs). In addition, pregnant females won’t eat as much.
  • Once you’ve identified a breeding pair, separate them from the other fish with a tank divider. Make sure that the end of the tank you choose for your breeding pair has everything they need. Always include enough plants and hiding spaces so that they will feel safe enough to mate.
  • In a community tank, you’ll have to remove the eggs. Otherwise, as the resulting fry grow, they will become vulnerable to predation. Using a specialist breeding slate for the eggs to attach to is best. Then you can simply lift it out of the tank.
  • You may find the parents love to lay eggs in plants. These help them feel secure that they and their eggs are safe from predation. If this happens you can try removing either all or part of the plant and placing it in a tank you’ve prepared for the fry.

Breeding In A Separate Tank:

Using a separate breeding tank can help prevent issues with aggression and other fish-eating angelfish eggs. However, tank dividers can accomplish the same things without requiring you to acclimatize your angelfish to a new environment. Angelfish prefer to keep things constant and too much change can make them stressed before breeding.

Looking After Koi Angelfish Fry:

Within the first few days after hatching, koi angelfish fry get nutrition from the yolk sacs of their eggs. After this period, they will be large and strong enough that they can feed on a specialist fry food (infusoria). Next, as they grow you can add in live protein, like bloodworms, white worms, and water fleas.

Final Thoughts

Are koi angelfish aggressive
In fact, they are much easier to look after than their exotic and delicate appearance might suggest. Image from Flickr

Although koi angelfish are a modern variety of angelfish that has been selectively bred to show specific colors, their needs are more or less the same as wild freshwater angelfish. Ultimately these are great fish to keep in a larger tank with a group of other angelfish, as well as shoals of compatible tankmates. In fact, they are much easier to look after than their exotic and delicate appearance might suggest.

Frequently Asked Questions

Are koi angelfish aggressive?
It can be confusing to hear these fish listed as both semi-aggressive and then to read information that says they are peaceful and need peaceful tankmates. Koi angelfish are generally only aggressive in territorial or hierarchical disputes towards other members of their own species - or towards species that can be seen as prey, like shrimps. Otherwise, they can peacefully coexist with many other tankmates such as tetras and other cichlids from the same environment. You can even minimize aggression by ensuring that they have enough spaces to hide, which is a way they solve disputes over territory and submissive fish can demonstrate this submissive behavior.
What is the difference between freshwater angelfish and saltwater?
The confusing naming of these two very different species of fish can sometimes mislead beginner aquarists! This article covers koi angelfish, a freshwater angelfish, which is found in the Amazon and Orinoco river basins and which comes from the genus pterophyllum. The most commonly kept species is pterophyllum scalare and this has actually been selectively bred to create different colors and patterns like the koi. As their differing names suggest, saltwater angelfish need saltwater and freshwater angelfish need freshwater. It’s important to never mix the two.
Are koi angelfish good for beginners?
Koi angelfish are not good fish for beginners, but fortunately, they’re not actually as hard to take care of as you might think from first looking at them. These are sensitive fish that require some former knowledge of keeping stable water parameters and ideally need someone who has experience with setting up community tanks due to their social nature and possible interactions with tankmates of other species. However, once you’ve got the hang of this, the individual natures of each fish and the way they naturally interact with their environment make them both fascinating and rewarding to keep.
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Sydney Perry

Sydney Perry has loved fish since she was a child and has enjoyed keeping many varieties over the years, ranging from black moors and shubunkins to betta fish. As a lover of nature and of Japanese culture, her dream tank is an Iwagumi aquascape, combining fish with carefully crafted aquatic landscapes in miniature.