In this article we will discuss about the diseases of aquarium fishes.

1. Degenerative Diseases:

Increasing age leads to heart failure, kidney failure, skeletal deformities, development of growth and pigmented tumours, imbalance, etc. Senile changes takes place and the fishes become incapable of breeding. Air-bladder disease is also common.

2. Traumatic Diseases:

Injuries due to fighting or popping out of the aquarium may lead to traumatic diseases.

3. Congenital Diseases:

Certain inborn deformi­ties (absence of gill covers, twisted backbone, etc.) leads to congenital diseases.

4. Sudden Shocks:


Aquarium fishes turns upside down, when transferred from acid to hard alkaline water. Similar shock symptoms are also observed in fishes when placed in water of different temperature.

5. Infectious Diseases:

Infectious diseases cau­sed mainly by protozoans are common in aquarium. Such diseases are transmitted through infected fishes either directly or at the time of transfer by a net.

Some common diseases witnessed are:

(i) White spot diseases:


Caused by the protozoan Ichthyophthirius sp., the white spot disease is very common infection in aquarium. It causes itching and the infected fish is seen to be rubbing its body against object in the aquarium to reduce irritation. They are often caused by a drop in water temperature.

A dip of the infected fish for ten days in 5% aquous solution of Methylene Blue is effective but should be applied in a tank where plants are absent, as methylene blue is harmful to plants.

(ii) Velvet disease:

Caused by the protozoan, Oodinium sp., velvet disease mostly affects labyrinth fishes and members of carp family such as Barbs, Minnows, Danios and live-bearing looth-carps. Fishes affected by this parasite have golden dust-like spots on their skin as if sprayed with golden powder.


Infected fry and young fishes usually succumb to the disease before it is determined. The free-swimming parasite is very difficult to irradicate as this protozoan also contains chlorophyll and can exist without fish for a long time in the presence of light.

Total treatment of the tank has to be done with Methylene Blue for ten days. The drug Acriflavin can also be used but it would cause temporary sterility in fishes. The plants in the infected tanks must be removed and washed in a solution of potassium permanganate. The gravel should be washed and preferably in boiling water.

(iii) Chilodon disease:

Caused by Chilodon cyprine, the protozoan parasite attaches itself to the skin ad gills of the fish resulting in asphyxiation. The affected fish is often seen to spiral up to the surface of the water to gasp a bubble of air. Treatment with Methylene Blue or Acriflavin may obtain favourable result.

(iv) Costiasis:

Costiasis results due to the infec­tion of the protozoan, costia sp., which grows on the mucus of the fishes, skin. The affected fishes lose their appetite, becomes lethargic and breaths heavily. A dip in 2.5% salt solution for fifteen minutes is recommended for cure.

(v) Fin rot:

The bacteria causing this disease enter through the damaged fin or inflammation and causes destruction of the fin tissue, resulting in death of the affected fish. Treatment with a weak solution of Acriflavin or Penicillin will be effective.

(vi) Columnaris disease:


Caused by Chondoccus columnaris, this bacteria enters the fishes’ body through injured areas, particularly near the mouth region. The cure recommended is 250 mg Chloram­phenicol capsule per gallon of water.

(vii) Pop-eye exophthalmos:

Aquarium with Siamese Fighting Fishes generally succumbs to this bacterial disease, when the eyes become swollen and cloudy. The affected fish loses its eye sight if not treated in time. The affected fighter fish is put in a net and one drop of silver eye drop is applied four times a day.

(viii) Cotton-wool disease:

Caused by the fun­gus Saprolegnia sp., the parasite attacks and grows at the region where damage of the skin has occurred It produces a cotton wool-like growth and the mycelia eventually invades the body tissue. The affected fishes should be removed and the wound treated daily with 50% Methylene Blue till its total irradication.

(ix) Infection by flukes:

Infection by flukes are caused by the trematodes, such as Gyrodactylus and Dactylogyrus that grow on the body and gills, respe­ctively. The infected fishes become pale with torn and slimy fins. The fishes should be kept in a blue solution of Methylene Blue for three days.

6. Enemies:

Fishes are also prone to attack by other animals and insects that accidentally enter into the aquarium through addition of pond water (through live food). The enemies are Hydra, Piscicola, Great Diving Beetle, Dragonfly larva, etc.