When you have an aquarium, one of the great doubts is learning to distinguish when one of the fish may not be healthy, and although it is complicated, these are ten prevalent diseases and the symptoms that can help identify them. Knowing these symptoms makes the situation more manageable.

Disease in the Middle

It may not be considered a disease, but many fish die when the PH rises above 9.0 or below 5.5. The decomposition of organic matter generates ammonia and nitrites that are very poisonous to fish, reason enough to cause their death

One of the main reasons is to neglect the filters, posing a great danger. Many times contact with toxic matter such as nicotine can cause problems. Another related but not so frequent thing is the excess oxygen in the water that would cause cardiac embolism.


It is mainly due to the absence of dissolved oxygen in the water. The symptoms that fish have are that they swim on the surface looking for the most superficial layer of air, although they usually do it without obtaining results. The only solution to this problem is to reduce the number of fish in the aquarium, and on the other hand, the aeration system of the aquarium should be checked.

Changes in Temperature

It usually occurs when there is a sudden temperature change. The symptoms that the fish present is that they gasp on the surface, swim pretty nervously and try to be near the water heater where the most abrupt changes occur while waiting for it to stabilize your body temperature.

The solution to this type of problem is to change the water in the aquarium and ensure that the water is at the same temperature. But, on the other hand, you should try not to place the aquarium where there are drafts. Depending on an aquarium of freshwater or saltwater, the temperature varies widely.

Virus and Bacteria

Sometimes the aquarium is not clean enough, and it can wreak havoc on the life of your fish. But, on the other hand, when a fish or other being in the water dies, it is necessary to try to remove its remains as soon as possible so as not to contaminate it. The most common disease is dropsy, especially bacterial fin rot.

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Chlorine Poisoning

The cause comes directly from the chlorine in the water, and the symptoms that fish present are the destruction of the gills, discoloration, paleness of the skin, sunken eyes, loss of coordination when swimming, and spasms. To remedy these consequences, the easiest thing to do is to remove the chlorine from the water before doing the water changes using specific products or by letting the water rest for at least 24 hours.


It sounds weird, but in the marine world, it also exists. The germ-bearing fish are the only source of contagion. But, on the other hand, the infection is transmitted by ingestion of infected material. The symptoms that appear are slow movements, weight loss, pale colors, falling scales, ulcers, and deformations of the jaws and spine.

Parasitic Worms

They can be both external and internal. For example, the flukes of the genera Dactylogyrus and Gyrodactylus parasitize fish’s gills, leaving them lifeless in a surprising way.

White Point

It is caused by the external protozoan Ichthyophthirius multifiliis. This parasite is responsible for commonly infecting the epidermis of the fins and gills. It feeds on the skin and tissues of the fish until they are mature enough. The usual thing is that it has the appearance of a white spot. It breaks the fish’s skin and goes into the water when it reaches maturity, causing epithelial erosion. Once free, the parasite becomes entrenched in the substrate, dividing until it produces up to 2,000 more individuals.

The fish’s symptoms are small white dots that give the fish dusted with sugar. When the stage is advanced, the bubbles coalesce and form yellowish spots.


The external metazoan Dactylogyrus causes it, usually attached to the gills, producing mucous hypersecretion. Its life cycle is direct. Their eggs are fixed on the gills of the fish that develop into a kind of spore. One of the most apparent symptoms is that they swim without practically moving. They rub against any object in the aquarium. Their body gives off a grayish mucus, their fins appear ragged, and sometimes they have ulcers.