10 common aquarium fish diseases- How to treat your aquarium fish

10 common aquarium fish diseases- How to treat your aquarium fish

Aquarium Fish Diseases – How to care and treat your aquarium fish?

Description of aquarium fish diseases

This section briefly examines the most common aquarium fish diseases, which, unfortunately, every aquarist faces. The section can not be used as a complete guide to the treatment of diseases. If you are seriously engaged in fish, then it makes sense to buy a good book – even if it is expensive, it will still be cheaper than replacing dead fish. If you just keep fish at home, then this section is probably enough for you.

The symptoms of the most common aquarium fish diseases are described here. It should be noted that the symptoms of many diseases are similar, besides, the fish can be affected by several diseases at once, because the weakened fish is easily affected, for example, by a bacterial infection. Therefore, sometimes the diagnosis is complicated, sometimes an autopsy is required (this issue is not considered here, because I do not know how to do this and I’m unlikely to learn) and various tests for gram-positive and gram-negative bacteria. In any case, if you are not sure of the diagnosis – consult a specialist. Do not treat immediately with a whole set of drugs just in case.

Ichthyophthirius (Ichthyophthirius, Ick, Ich, white spot)

The most of one common aquarium fish diseases. White cysts up to 1 mm in size appear on the fish. Sometimes they form clusters – as if they sprinkled fish with sugar. Slaves scratching on different objects. Often there is a secondary bacterial infection. Each cyst is a parasite’s nest – Protozoa, which after the ripening leaves the body of the fish and, within a few hours, forms around itself a capsule in which the cells begin to divide and, then, look for a new host. If they did not find the master, then the parasite perishes.

10 common aquarium fish diseases- How to treat your aquarium fish

The life cycle of the parasite is 7-10 days at a temperature of 21 ° C, and at a temperature of 10 ° C – several weeks. All medicines are designed to destroy free-floating parasites. Inside the cysts on the body of the fish, medicines do not work.

Usually cysts are present in any aquarium, but they are affected only by weakened fish.


Treatment is very easy if the disease is not started. You can use one of the brand-name drugs designed to treat this disease. Some catfish and other fish, such as clown loach, are sensitive to such drugs, so carefully follow the instructions. The following preparations are usually used,

Malachite greens are the most common drug for treating ich. Different firms use a different concentration of the drug, so follow the instructions. When using this drug, like everyone else, it is necessary to withstand the full course of treatment, usually about 7-10 days. This ensures that all ripened and hatched parasites will be destroyed by the drug. Otherwise, it may turn out that the fish will be infected again a few days after the end of treatment. This drug can be used several times without causing side effects.

Quinine – is used in the form of sulfate or hydrochloride

Antibiotics – usually ineffective against parasites

Another way is to raise the temperature to 30-32 ° C, while free-floating parasites die. It is useful to add salt 1-3 g / l. Water should be aerated and changed, because at this temperature there is little oxygen in it. The method is very effective and has much fewer side effects.

A similar parasite causes a disease that is mainly affected by guppies. Along with white points, loss of scales and unusual behavior of fish are observed. The disease is treated with simple brand-name preparations.


The main symptom of this aquarium fish disease is the unnaturally bulging eyes of fish (telescopes and similar fish do not belong here). Similar signs are also encountered in tuberculosis. This disease is caused by various factors – poor water quality, bacterial infection, etc. Usually, the disease affects one or two fish in the aquarium, sometimes it goes through some time. If suddenly a lot of fish are sick, then you should check the water quality or it can be caused by a contagious microorganism.

10 common aquarium fish diseases- How to treat your aquarium fish

Treatment is made by one of the branded drugs for the treatment of bacterial infection. Since the disease is rarely contagious, the other way is to isolate the fish and observe it.

Fungal and bacterial infections (saprolegnia, fungus, fin rot)

The aquarium fish diseases is caused by bacteria, such as Aeromona, Pseudomonas and various mycobacteria. Causes of the disease can be inaccurate handling of fish during transportation, with the fins biting more aggressive fish, poor water quality, etc. In the beginning, the fins look glued, then a white coating appears on them and they are destroyed.

10 common aquarium fish diseases- How to treat your aquarium fish

It is easy to be treated with brand-name drugs. Addition of salt to the water is one of the methods of preventing this disease in viviparous fish, for example, guppies. With timely treatment, the tail and fins then grow again.

In the photo there is a fish with a fungal disease (it looks like mold). It is caused by bacteria such as Saprolegnia, Achlya, etc. Spores of these bacteria are usually always present in the aquarium, but healthy fish are immune to such diseases and the protective layer of mucus covering the body of the fish is a baoyell for them. Only if there is a favorable environment for the development of such spores, for example, the fish are weakened by stress, poor water quality , A lot of rotting organic in the aquarium, the protective layer of mucus on the fish is damaged, as a result of rough handling, physical damage, etc. The outbreak of the disease occurs. Fungus can also infect fish eggs.

Treatment is made by one of the branded preparations, methylene blue, malachite greens, etc.

Hole-in-the-head (Hexamytosis)

10 common aquarium fish diseases- How to treat your aquarium fish

Small depressions are formed on the body, especially on the head. Often these ulcers are covered with a layer of mucus. Over time, these ulcers increase, leading to the death of fish. The aquarium fish disease is caused by the bacteria Hexamita. The disease affects more cichlids, discus, astronotus and gourami. The exact causes of the disease are unknown and the bacteria present in the aquarium water are almost always in small amounts. It is assumed that outbreaks are associated with malnutrition (in particular, vitamin C deficiency) and water quality, for example, it is believed that filtering water with activated carbon removes many substances from the water, contributing to the development of the disease.

The usual method of treatment is the use of medicines added to food. There are also a number of drugs for the treatment of this disease (eg, preparations containing dimetridazole and metronidazole). Usually these preparations are very strong and if you have small fish in the aquarium, then they must be removed. Frequent water changes and a balanced diet are a good way to prevent disease.


The fish looks swollen and scales stand on end like a Christmas tree. The aquarium fish disease is caused by various bacteria and metabolic disorders. The disease occurs in fish that are in poor conditions, although it can infect one and two fish in a well-groomed aquarium. A similar disease occurs in African cichlids, it is called malawi bloat.

10 common aquarium fish diseases- How to treat your aquarium fish

Treatment is done by one special medication. For larger fish, the veterinarian can suck excess fluid from the fish. Sometimes, it is possible, having planted a fish and containing it under ideal conditions, to cure fish without medicines.


The aquarium fish disease is caused by bacteria, such as Mycobacterium and Nocardia. The fish looks drained, often afflicted by secondary bacterial and fungal infections, the eyes are bulging and ulcers are formed on the body and internal organs. It is believed that the infection of fish occurs through the feed, although other methods are possible. Therefore, one should be especially careful when using fodder fish, since they are often kept in very poor conditions.

10 common aquarium fish diseases- How to treat your aquarium fish

The treatment is extremely difficult and requires expensive drugs (containing sulfafurazole, minocycline, etc., so it is best to kill the diseased fish painlessly, if after quarantining to the quarantine aquarium, its condition has not improved. To prevent the disease, acquire new fish only from a healthy aquarium and quarantine their.

A number of bacteria from the Mycobacterium genus can be transmitted to people, causing various skin diseases, etc. Therefore, avoid contact with unprotected skin, especially with open scratches, etc., use gloves. After an outbreak of disease, always disassemble the equipment.

Ulcers on the body of fish

10 common aquarium fish diseases- How to treat your aquarium fish

The aquarium fish disease is caused by the bacteria Aeromonas, etc. On the body of fish and internal organs ulcers appear. These bacteria are usually present in small quantities in the aquarium and with poor water quality, an outbreak occurs. Most often the disease affects zoototyh fish, although it also occurs in tropical fish.

Velvet disease (Oodinium)

This aquarium fish diseases is caused by parasites – Oodinium. The body of the fish is covered with yellowish-gray dots. Points resemble ichthyophthirius, but they are smaller in size and the fish looks as if sprinkled with golden dust. Fish scratching on various objects in the aquarium, often breathing gills. Sometimes with her stripes comes off the skin. The cycle of the parasite is similar to that of the ichthyothyroid cycle, but the parasite can exist for a long time without a host.

Treatment can be difficult if the parasites have settled in the internal organs of the fish. The disease is contagious, so it is best to plant sick fish.

Treatment is made by one of the branded products. An increase in temperature that does not kill parasites helps but speeds up the cycle of their maturation, shortening the time that they can live without the host.

The drugs for the treatment of this disease usually include the following components:

Acriflavin (Acriflavin) – one of the most effective drugs for treatment. To increase the efficiency it is recommended to raise the temperature and add salt. It can not be used for a long period, as this can cause problems with the reproduction of some fish

Copper sulfate and other copper compounds are effective against the causative agents of this aquarium fish diseases. Usually the dose is about a drop per liter of water for 1% solution (however always follow the manufacturer’s instructions). The dose should be repeated after three days. Filtering with activated carbon should be turned off. After finishing the course of licking, water can be purified by filtration through coal. Copper is toxic to fish and if you notice that the fish capture air bubbles or show other signs of stress, then treatment should be discontinued.

Colonariosis (oral rot)

Oral rot, or oral fungus, despite the name, is actually a bacterial disease and is usually confined to the oral cavity. Bacteria – pathogens form colonies in the form of long filaments that look very much like a fungus. Therefore, if you notice a fungus that is confined mainly to the oral cavity, it is most likely a mouth rot, and you need to treat it accordingly, and not like a fungus. If you want to keep the fish alive, then the treatment should be carried out immediately.

Parasites in the entrails of fish

10 common aquarium fish diseases- How to treat your aquarium fish

Worms in the body cavity – the aquarium fish diseases can be caused by various types of worms, ranging from the smallest ones to the length of a few meters reaching large fish. Symptoms are a swollen abdomen in a fish, a mediocre swimming, sometimes worms are visible from the anus, sometimes they break through the body of the fish.

Worms in the body cavity are found only in newly imported fish. Due to their complex development cycle, which includes several hosts, this aquarium fish diseases does not reach a dangerous level in aquariums. Treatment is almost impossible. Try not to buy fish with similar symptoms.

10 common aquarium fish diseases- How to treat your aquarium fish

Chewri in the digestive system include – nematodes, cestodes, etc. Unfortunately, it is possible to put a definite diagnosis with a neglected aquarium fish disease, when the fish looks depleted, the worms are visible from the anus, etc. Some worms are usually recorded with new fish and are not transferred to other fish because of the complexity of the development cycle. However, Camallanus nematodes (up to 2 cm long, round worms) are a common parasite in viviparous tropical fish and are a problem, since they can be transferred from fish to fish without an intermediate host. They are treated with one of the brand-name preparations.


Author: Admin

James Walker has been a passionate aquarist for over 15 years. His fascination with underwater ecosystems began as a child, and he's since dedicated himself to learning about proper fish care, aquarium design, and the diverse world of freshwater species. James loves sharing his knowledge to help others build thriving aquatic environments.

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