Why are my angelfish’s eyes red?

In this post, we will answer the question “Why are my angelfish’s eyes red?”. We will discuss the possible causes of angelfish’s eyes turning red and also if this could be natural for angelfish.

Why are my angelfish’s eyes red?

Some angelfish species have red eyes as a result of their genetic makeup. Similarly, because albino angelfish lack dark pigments, their eyes are pink or red, much like the eyes of all other albino animals. It is possible to have red or bloodshot eyes due to a health concern, such as viral hemorrhagic septicemia or an accident. Angelfish can have bloodshot eyes if they have been poisoned by ammonia, nitrate, or CO2.

The colour of an angelfish’s eyes can change from time to time, but this does not happen very often. If the eyes are red from birth, this will likely be the colour that they will be throughout life.

What does it mean when a fish has red eyes?

Red eyes in angelfish are quite natural in the vast majority of instances. As previously indicated, certain species, such as the zebra angelfish, have red eyes that develop naturally in their eyes. It is a sign of excellent health and maturity, and there is no reason to be concerned about it at this time. 

Angelfish eyes can change colour as a result of environmental variables such as stress or changes inside the tank, even though this is a rare occurrence. When things return to normal, the colour of the eyes should revert to its original shade of blue. 

Red eyes, on the other hand, can be a symptom of a health condition, especially if they’ve changed colour from something clear to red in the blink of an eye. From an early age, you will be able to tell whether your fish’s eyes are intended to be red since they will acquire red pigmentation in their eyes. If the colour of the eyes appears to change seemingly overnight, then something is amiss. 

When fish have bloodshot or red eyes, it is important to address the issue as soon as possible to avoid the fish becoming ill. Once fish become ill, their condition rapidly deteriorates. The following are some of the most prevalent causes of red eyes in fish:


According to what has previously been stated, stress can cause an angelfish’s eyes to become red. It can also affect the colour of the scales and stripes on its body. The removal of the source of the angelfish’s stress should aid in the restoration of the colour of the eyes to their original state. Fish that are stressed will exhibit the following symptoms: 

• Gasping at the surface of the tank 

• Lack of appetite or reluctance to feed 

• Disease (typically marked by red eyes and white patches on the fish’s body) 

• Frenetic swimming and unusual swimming patterns 

Stress may be caused by a variety of situations in an angelfish’s life. They can be any of the following:

      Poor water conditions

If the water in which your angelfish lives is not properly kept, your fish may have difficulty breathing. Stress is caused by low oxygen levels, excessive amounts of ammonia or nitrate, or water that is too hot or too cold to drink. pH levels that are too low or too high are also problematic. 

You will need to run a water test to determine the specific origin of the problem. After you’ve resolved the problem, your angelfish should return to their normal state, with their eyes reverting to their natural hue.


Tanks that are overflowing with fish don’t provide enough space for the fish to swim around in. Angelfish are territorial species that will engage in territorial battles with other fish to establish control. This is distressing for every one of the fish involved, including the ones that are being harassed into compliance. 

While small groups of angelfish are more prone to result in bullying because one or two fish are singled out, a tank with 5 angelfish is the optimal quantity to avoid this problem. It enables them to form a school and protects other fish from being picked off by the school.

      Improper diet

You may notice your angelfish becoming upset due to lack of food if it is not receiving enough food. Overfeeding is harmful to fish, thus many fish keepers make the mistake of unwittingly underfeeding their fish. 

Allow each angelfish around 30 seconds worth of eating time when you are feeding them. This shows that they have received sufficient nourishment. Any more would be excessive, and any less would be insufficient. 

If angelfish do not consume enough food, they become aggressive and battle for the food that is available. As a result, the normally tranquil fish in the tank become afraid and stressed, and these are the ones that are most likely to get red eyes out of all of your angelfish, according to the research.

      Loud noises

This is especially problematic if you have little children in the house who are constantly banging on the tank’s glass. This causes great stress to the angelfish, which is most noticeable while they are trying to sleep. 

As an example, placing the tank in a room with a lot of background noise may generate too much disruption, resulting in your angelfish’s eyes being flushed. 

Keep little children away from the tank when they are not being watched and emphasise the necessity of treating angelfish with courtesy. 

Also, when putting up your tank, make sure it is in the most peaceful location possible in your home so that the angelfish may live in peace.

Chemicals in the water

Something in your angelfish’s water might be causing their eyes to get bloodshot and red, which could be causing them to become irritated. 

If toxic water is not handled, it can result in poisoning. It enters the fish’s system through its gills and travels fast into the bloodstream, where it causes considerable harm to the animal. As a haemorrhage or rupture occurs, the eyes of an angelfish become red due to high quantities of toxin.


Ammonia is a chemical that is poisonous to fish. Ammonia poisoning can be caused by a variety of factors, including new setups, hazardous microbes, and changes in the bio-load. The following factors contribute to its development: 

– Chemically treated tap water

– Decomposition of plants, faeces, and uneaten fish food 

– A build-up of bacteria is caused by overfeeding and a lack of proper cleaning. 

– Angelfish that have been poisoned linger near the bottom of the tank, seemingly lifeless. Internal and external bleeding, as well as red eyes that appear as red spots on the body, are possible side effects of this condition. 

Make certain that the pH of the water is at a safe level to prevent ammonia poisoning. This value ranges between 6.8 and 7.8 for angelfish. Ammonia discovered at this concentration is non-toxic, however, anything greater than this can be lethal. Reduce the ammonia concentration to less than 1 part per million (ppm) by changing 50 per cent of the water at the same temperature as the remainder of the aquarium.


Nitrite poisoning (also known as brown blood illness) causes a fish’s blood to become brown as a result of elevated amounts of methemoglobin in the blood. The eyes of several fish have turned red as a result of nitrite poisoning, according to their owners. 

Fish are known to be hazardous to nitrite, according to a report published by the Fresenius Environmental Bulletin. Although it is not as hazardous as ammonia, it may still create a variety of health problems in fish if it is allowed to influence them for an extended length of time. 

It occurs most frequently when the aquarium is first set up. Ammonia is excreted by fish through their gills. The ammonia is converted to nitrite by the presence of beneficial microorganisms in the tank. A well-established tank includes helpful bacteria that feed on ammonia and convert it to a non-toxic waste product. 

In new tanks that haven’t had time to cycle, ammonia can build up in areas where there aren’t enough bacteria to turn it into nitrogen gas. Nitrite poisoning happens as a result of this. 

After entering the fish’s bloodstream, large amounts of nitrite will eventually cause the fish to suffocate due to the lack of oxygen. Before that happens, you’ll notice fish struggling for breath in the water. Their eyes may turn red in the most severe situations. 


It is fatal because CO2 poisoning is hazardous and develops fast, which is why it is so common. When there is too much in the tank, the fish begin to suck for oxygen at the surface and become sluggish. They finally succumb to suffocation. CO2 concentrations of more than 25-30 parts per million (ppm) are hazardous. 

The most likely reasons for this are faulty CO2 reactors or a shortage of plants in the tank to absorb the CO2. In a similar vein, a mistake by the operator results in an excessive amount of CO2 in the tank. Surface agitation and air stones are used to aerate the water to remove excess CO2 from it.


Angelfish red eyes are caused by a variety of factors, the most frequent of which is injury. Especially when purchasing from unreputable breeders that don’t exercise caution while handling the fish, it is normal to see the fish being handled. 

In a similar vein, angelfish that battle may occasionally assault each other’s eyes. The accumulation of blood in the eye after a serious injury causes red spots or bloodshot eyes where the arteries have ruptured. 

Fish eye injuries are extremely difficult to treat. Most of the time, they will go away on their own, but adding 1 to 3 teaspoons of Epsom salts per gallon of water will assist to alleviate the swelling. 

If they do not, it is possible that an infection has taken hold and that veterinarian care will be required. Keep a watch on the eye to see whether the redness subsides – this is an indication that the wound is healing well.


In this post, we answered the question “Why are my angelfish’s eyes red?”. We discussed the possible causes of angelfish’s eyes turning red and also if this could be natural for angelfish.

If you have any thoughts or doubts, feel free to drop us a comment below!

Frequently Asked Questions (FAQs): Why are my angelfish’s eyes red?

What is the cause of my angelfish’s red eyes? 

The presence of a red eye in angelfish may indicate that it is fully mature and in good health. Red eyes, on the other hand, may signify some forms of health concerns or intoxication. 

What is the name of the most endangered freshwater angelfish? 

The Clown Angelfish is one of the rare breeds of Angelfish, and it may be difficult to locate one without putting forth significant effort on your part. These fish have a complicated pattern that runs over their entire body, resulting in spots that are different in size and form from one another. Clown Angelfish are more tranquil than many other varieties of angelfish, and they are also rather simple to keep. 

What are a red Devil angelfish, and where can I find one? 

The Red Devil or Super Red Angel (Pterophyllum scalare) is a remarkable and unusual line bred variety of the common Angel (Pterophyllum scalare), and it is a popular variation owing to its bright deep red hue. They thrive in a large, tall, planted aquarium with plenty of hiding places, just like all other angels. 

What are the most expensive angelfish you’ve ever seen? 

The peppermint angelfish is renowned as one of the most expensive fish in the world, with the highest stated price being $30,000 for a peppermint angelfish. And there’s a compelling argument in support of it! A trained diver must descend nearly 400 feet into the ocean to collect these fish, which is a special requirement for this species.


Gómez-Laplaza, L. M., & Gerlai, R. (2013). Quantification abilities in angelfish (Pterophyllum scalare): the influence of continuous variables. Animal Cognition, 16(3), 373-383.

Why Does My Angelfish Have Red Eyes? https://www.justfishkeeping.com/angelfish-with-red-eyes/