Ornamental fish kept in

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

s are susceptible to numerous

diseases A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that ar ...

. Due to their generally small size and the low cost of replacing diseased or dead fish, the cost of testing and treating diseases is often seen as more trouble than the value of the fish. Aquarium Nitrogen Cycle

Due to the artificially limited volume of water and high concentration of fish in most

tanks,

communicable disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

s often affect most or all fish in a tank. An improper

nitrogen cycle The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biologi ...

, inappropriate aquarium plants and potentially harmful freshwater invertebrates can directly harm or add to the stresses on ornamental fish in a tank. Despite this, many diseases in captive fish can be avoided or prevented through proper water conditions and a well-adjusted ecosystem within the tank.

Causes

Diseases can have a variety of causes, including bacterial infections from an external source such as ''

Pseudomonas fluorescens ''Pseudomonas fluorescens'' is a common Gram-negative, rod-shaped bacterium. It belongs to the ''Pseudomonas'' genus; 16S rRNA analysis as well as phylogenomic analysis has placed ''P. fluorescens'' in the ''P. fluorescens'' group within the genu ...

'' (causing

fin rot A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

and

fish dropsy Dropsy is a condition in fish caused by the buildup of fluid inside the body cavity or tissues. As a symptom rather than a disease in its own right, it can indicate a number of underlying diseases, including bacterial infections, parasitic infect ...

), fungal infections ( Saprolegnia),

mould A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. No ...

infections ( Oomycete and '' Saprolegnia''), parasitic disorders ('' Gyrodactylus salaris'', '' Ichthyophthirius multifiliis'',

Cryptocaryon ''Cryptocaryon irritans'' is a species of ciliates that parasitizes marine fish, causing marine white spot disease or marine ich (pronounced ''ick''). It is one of the most common causes of disease in marine aquaria. Taxonomy ''Cryptocaryon i ...

, Oodinium causing velvet disease, ''

Brooklynella hostilis ''Brooklynella hostilis'' is a parasite of marine fish, found in wild fish, farmed fish and aquariums. It is kidney-bean shaped, and approximately 60–80 μm long, with bands of cilia. ''B. hostilis'' is the only species in the monotypic ta ...

'',

head and lateral line erosion Head and lateral line erosion, (HLLE) or hole-in-the-head (HITH) is a disease in fish. Chronic ulcerative dermatopathy or chronic erosive dermatopathy are symptoms of similar conditions with different etiology. Symptoms HLLE begins as small pits ...

Glugea ''Glugea'' is a genus of microsporidian parasites, predominantly infecting fish. Species include * ''Glugea anomala'' * ''Glugea atherinae'' * ''Glugea capverdensis'' - a parasite of the fish ''Myctophum punctatum'' * ''Glugea caulleryi'' - a p ...

, ''

Ceratomyxa shasta ''Ceratonova shasta'' (syn. ''Ceratomyxa shasta'') is a myxosporean parasite that infects salmonid fish on the Pacific coast of North America. It was first observed at the Crystal Lake Hatchery, Shasta County, California, and has now been reporte ...

'', ''

Kudoa thyrsites ''Kudoa thyrsites'' is a myxosporean parasite of marine fishes. It has a worldwide distribution, and infects a wide range of host species. This parasite is responsible for causing economic losses to the fisheries sector, by causing post-mortem ...

'', ''

Tetracapsuloides bryosalmonae ''Tetracapsuloides bryosalmonae'' is a myxozoan parasite of salmonid fish. It is the only species currently recognized in the monotypic genus ''Tetracapsuloides''. It is the cause of proliferative kidney disease (PKD), one of the most serious par ...

'', ''

leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...

es,

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

, Trematoda, Platyhelminthes and

fish louse The family (biology), family Argulidae, whose members are commonly known as carp lice or fish lice, are parasite, parasitic crustaceans in the class Ichthyostraca. It is the only family in the monotypic subclass Branchiura and the order Arguloid ...

viral Viral means "relating to viruses" (small infectious agents). Viral may also refer to: Viral behavior, or virality Memetic behavior likened that of a virus, for example: * Viral marketing, the use of existing social networks to spread a marke ...

disorders, metabolic disorders, inappropriate water conditions (insufficient aeration, pH,

water hardness Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbo ...

, temperature and

ammonia poisoning {{About, ammonia poisoning in fish and aquariums, ammonia toxicity in humans, Hyperammonemia Ammonia poisoning is a common fish disease in new aquariums, especially when immediately stocked to full capacity. Ideally, the level of ammonia (NH3) ...

) and malnutrition. External bacterial infections may cause spots or streaks on the body which appear red or orange Dropsy (bloating) is also a sign of a bacterial infection. "False

fungal infections Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ti ...

" look like fungus but is actually a bacterial infection known as

Columnaris Columnaris (also referred to as cottonmouth) is a symptom of disease in fish which results from an infection caused by the Gram-negative, aerobic, rod-shaped bacterium ''Flavobacterium columnare''. It was previously known as ''Bacillus columnaris, ...

. These symptoms may include a white or gray film on the body.

Prevention

Disease cures are almost always more expensive and less effective than simple prevention measures. Often precautions involve maintaining a stable aquarium that is adjusted for the specific species of fish that are kept and not over-crowding a tank or over-feeding the fish. Common preventive strategies include avoiding the introduction of infected fish, invertebrates or plants by

quarantining A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

new additions before adding them to an established tank, and discarding water from external sources rather than mixing it with clean water. Similarly, foods for

herbivorous fish A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

such as lettuce or

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated Vine#Horticultural climbing plants, creeping vine plant in the Cucurbitaceae family that bears usually cylindrical Fruit, fruits, which are used as culinary vegetables.

s should be washed before being placed in the tank. Containers that do not have water filters or

pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they u ...

s to circulate water can also increase stress to fish. Other stresses on fish and tanks can include certain chemicals, soaps and

detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...

s, and impacts to tank walls causing shock waves that can damage fish.

Treatment

In some cases the causes of an infection or disease will be obvious (such as fin rot), though in other cases it may be due to water conditions, requiring special testing equipment and chemicals to appropriately adjust the water. Isolating diseased fish can help prevent the spread of infection to healthy fish in the tank. This also allows the use of chemicals or drugs which may damage the nitrogen cycle, plants or chemical filtration of a properly-functioning tank. Other alternatives include short baths in a bucket that contains the treated water. Salt baths can be used as an antiseptic and

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

, and will not damage beneficial bacteria, though ordinary table salt may contain additives which can harm fish. Alternatives include aquarium salt, Kosher salt or rock salt. Gradually raising the temperature of the tank may kill certain parasites, though some diseased fish may be harmed and certain species can not tolerate high temperatures. Aeration is necessary since less oxygen is dissolved in warm water. There are a number of effective treatments for many strains of bacterial infections. Three of the most common are tetracycline,

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

and naladixic acid. Salt baths are another effective treatment.

References

* * * * {{fish disease topics Fish diseases Fishkeeping

Causes

Prevention

Treatment

See also

References