Nitric acid test and paper chromatography test are used in the detection of argemone oil.Paper chromatography test is the most sensitive test.

Quaternary ammonium compounds can be added to the water of infected adult fish and fry. Alternatively, the antibiotic oxytetracycline can be given to adults, fry and broodstock. To prevent the disease, it is necessary to ensure water is pathogen-free and that water hardening is completed effectively for eggs.

Currently, the most effective treatment is transferring the affected fish to a freshwater bath for a period of 2 to 3 hours. This is achieved by towing the sea cages into fresh water, or pumping the fish from the sea cage to a tarp filled with fresh water. Mortality rates have been lowered by adding Levamisole to the water until the saturation is above 10ppm. Due to the difficulty and expense of treatment, the productivity of salmon aquaculture is limited by access to a source of fresh water. Chloramine and chlorine dioxide have also been used. Other potential in-feed treatments such as immunosupportive-based feeds, mucolytic compounds such as L-cysteine ethyl ester and the parasticide bithionol have been tested with some success although not developed for commercial use.

Electron microscopy can reveal the bullet-shaped rhabdovirus, but is not

adequate for definitive diagnosis.

The Manual or Diagnostic for Aquatic Animals, 2006, is the standard

reference for definitive tests. In most cases, cell culturization

is recommended for surveillance, with antibody tests and reverse transcription

polymerase chain reaction (RT-PCR) and genetic sequencing and comparison

for definitive confirmation and genotype classification.

Virus neutralisation is another important method of diagnosis, especially for carrier fish.

Several antibiotics are available for the treatment of redmouth disease in fish. Vaccines can also be used in the treatment and prevention of disease. Management factors such as maintaining water quality and a low stocking density are essential for disease prevention.

Currently, no treatment is available.

Good husbandry measures, such as high water quality, low stocking density, and no mixing of batches, help to reduce disease incidence. To eradicate the disease, very strict protocol with regards to movement, water sources and stock replacement must be in place – and still it is difficult to achieve and comes at a high economic cost.

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, 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 stains of bacterial infections. Three of the most common are tetracycline, penicillin and naladixic acid. Salt baths are another effective treatment.

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 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 such as lettuce or cucumbers should be washed before being placed in the tank. Containers that do not have water filters or pumps to circulate water can also increase stress to fish. Other stresses on fish and tanks can include certain chemicals, soaps and detergents, and impacts to tank walls causing shock waves that can damage fish.

Infected fish should be moved into high quality water, where they may recover if their clinical signs are mild.

If disease occurs eradication is required. Once the disease is eradicated good husbandry, surveillance and biosecurity measures are necessary to prevent recurrence. In countries free of epizootic ulcerative syndrome, quarantine and health certificates are necessary for the movement of all live fish to prevent the introduction of the disease.

Preliminary diagnosis involves histopathological examination,

observing tissues through a microscope. Most tissue changes can be observed

as minor to major necrosis (cell death) in the liver, kidneys, spleen, and

skeletal muscle. The hematopoietic (blood-forming) areas of the kidney and

spleen are the initial area of infection, and should show necrosis.

The gill may have thickened lamellae, and the liver may have pyknotic nuclei.

Skeletal muscle accumulates blood but does not suffer much damage.

By the time a disorder reaches the point of causing dropsy, it can often be fatal and at the very least the fish is very ill and requires immediate quarantine and treatment.

As "Flavobacterium columnare" is Gram-negative, fish can be treated with a combination of the antibiotics furan-2 and kanamycin administered together. A medicated fish bath (using methylene blue or potassium permanganate and salt), is generally a first step, as well lowering the aquarium temperature to 75 °F (24 °C) is a must, since columnaris is much more virulent at higher temperatures, especially 85–90 °F.

Medicated food containing oxytetracycline is also an effective treatment for internal infections, but resistance is emerging. Potassium permanganate, copper sulfate, and hydrogen peroxide can also be applied externally to adult fish and fry, but can be toxic at high concentrations. Vaccines can also be given in the face of an outbreak or to prevent disease occurrence.

In Northern Australia, where ciguatera is a common problem, two different folk science methods are widely believed to detect whether fish harbor significant ciguatoxin. The first method is that flies are supposed not to land on contaminated fish. The second is that cats will either refuse to eat or vomit/display symptoms after eating contaminated fish. A third, less common testing method involves putting a silver coin under the scales of the suspect fish. If the coin turns black, according to the theory, it is contaminated.

On Grand Cayman and other islands the locals will test barracuda by placing a piece of the fish on the ground and allowing ants to crawl on it. If the ants do not avoid the flesh and will eat it, then the fish is deemed safe.

In Dominican Republic, another common belief is that during months whose names do not include the letter "R" (May through August), it is not recommended to eat certain kinds of fish, because they are more likely to be infected by the ciguatera toxin.

The validity of many of these tests has been scientifically rejected.

Withdrawal of the contaminated cooking oil is the most important initial step. Bed rest with leg elevation and a protein-rich diet are useful. Supplements of calcium, antioxidants (vitamin C and E), and thiamine and other B vitamins are commonly used. Corticosteroids and antihistaminics such as promethazine have been advocated by some investigators, but demonstrated efficacy is lacking. Diuretics are used universally but caution must be exercised not to deplete the intravascular volume unless features of frank congestive cardiac failure are present, as oedema is mainly due to increased capillary permeability. Cardiac failure is managed by bed rest, salt restriction, digitalis and diuretics. Pneumonia is treated with appropriate antibiotics. Renal failure may need dialysis therapy and complete clinical recovery is seen. Glaucoma may need operative intervention, but generally responds to medical management.

Sodium chloride is believed to mitigate the reproduction of Velvet, however this treatment is not itself sufficient for the complete eradication of an outbreak. Additional, common medications added directly to the fish's environment include copper sulfate, methylene blue, formalin, malachite green and acriflavin, all of which can be found in common fish medications designed specifically to combat this disease. Additionally, because Velvet parasites derive a portion of their energy from photosynthesis, leaving a tank in total darkness for seven days provides a helpful supplement to chemical curatives. Finally, some enthusiasts recommend raising the water temperature of an infected fish's environment, in order to quicken the life cycle (and subsequent death) of Velvet parasites; however this tactic is not practical for all fish, and may induce immunocompromising stress.

Because dropsy is a symptom of an illness, its cause may or may not be contagious. However, it is standard practice to quarantine sick fish to prevent spreading the underlying cause to the other fish in the tank community.

Symptoms typically begin to appear two months after the fish are transferred from freshwater hatcheries to open net sea cages. Symptoms include mucus build-up on the gills of infected fish and hyper-plastic lesions, causing white spots and eventual deterioration of the gill tissue. Fish will show signs of dyspnoea such as rapid opercular movements and lethargy. Although usually recognised by hyperplastic and proliferative gill lesions, the effects of AGD occur before oxygen transfer across the gill is severely compromised. AGD affected fish show a significant increase in vascular resistance contributing to cardiovascular collapse. Such effects result in compensatory changes in heart shape to improve its efficiency at pumping blood.

Contributing factors are an ambient water temperature above 16 degrees Celsius, crowding and poor water circulation inside the sea pens. Clinical cases are more common in the Summer. The lesions on the gills are highly suggestive of infection. Gill biopsies can be observed under the microscope for amoebas, or tested using fluorescent antibody testing.

Infection can cause subcutaneous haemorrhage that presents as reddening of the throat, mouth, gill tips, and fins, and eventual erosion of the jaw and palate. Hemorrhaging also occurs on internal organs, and in the later stages of the disease, the abdomen becomes filled with a yellow fluid - giving the fish a "pot-bellied" appearance. The fish often demonstrate abnormal behavior and anorexia. Mortality rates can be high.

A presumptive diagnosis can be made based in the history and clinical signs, but definitive diagnosis requires bacterial culture and serological testing such as ELISA and latex agglutination.

Ulcerations develop within 24 to 48 hours. Fatality occurs between 48 and 72 hours if no treatment is pursued; however, at higher temperatures death may occur within hours. Other symptoms may accompany the disease, including lethargy, color loss, redness around the infection site, loss of appetite and twitching or rubbing the body against objects.

Fish infected with typical BCWD have lesions on the skin and fins. Fins may appear dark, torn, split, ragged, frayed and may even be lost completely. Affected fish are often lethargic and stop feeding. Infection may spread systemically. Salmonid fish can also get a chronic form of BCWD following recovery from typical BCWD. It is characterised by erratic “corkscrew” swimming, blackened tails and spinal deformities.

In rainbow trout fry syndrome, acute disease with high mortality rates occurs. Infected fish may show signs of lethargy, inappetance and exopthalmos before death.

A presumptive diagnosis can be made based on the history, clinical signs, pattern of mortality and water temperature, especially if there is a history of the disease in the area. The organism can be cultured for definitive diagnosis. Alternatively, histology should show periostitis, osteitis, meningitis and ganglioneuritis.

Various Caribbean folk and ritualistic treatments originated in Cuba and nearby islands. The most common old-time remedy involves bed rest subsequent to a guanabana juice enema. Other folk treatments range from directly porting and bleeding the gastrointestinal tract to "cleansing" the diseased with a dove during a Santería ritual. In Puerto Rico, natives drink a tea made from mangrove buttons, purportedly high in B vitamins, to flush the toxic symptoms from the system. There has never been a funded study of these treatments.

An account of ciguatera poisoning from a linguistics researcher living on Malakula island, Vanuatu, indicates the local treatment: "We had to go with what local people told us: avoid salt and any seafood. Eat sugary foods. And they gave us a tea made from the roots of ferns growing on tree trunks. I don't know if any of that helped, but after a few weeks, the symptoms faded away."

Senescent leaves of "Heliotropium foertherianum" (Boraginaceae), also known as octopus bush, a plant used in many Pacific islands as a traditional medicine to treat ciguatera fish poisoning, contain rosmarinic acid and derivatives, which are known for their antiviral, antibacterial, antioxidant and anti-inflammatory properties. Rosmarinic acid may remove the ciguatoxins from their sites of action, as well as being an anti-inflammatory.

Treatment is in the form of supportive care. If there is light-headedness, the victim should lie with feet partly elevated. If there is severe wheezing, then intramuscular epinephrine should be given, 0.5–1 ml at dilution of 1/1000 (standard medical emergency kit). An intravenous antihistamine like diphenhydramine should be given if needed.

A sharp rise in mortality is often seen (depending on the virulence of the disease). Other clinical signs include abdominal swelling, anorexia, abnormal swimming, darkening of the skin, and trailing of the feces from the vent. On necropsy, internal damage (viral necrosis) to the pancreas and thick mucus in the intestines often is present. Surviving fish should recover within one to two weeks.

Diagnostic methods for the detection of the disease include: characteristic histological pancreatic lesion, PCR, indirect fluorescent antibody testing, ELISA, and virus culture. High virus titers can be isolated from carrier animals.

Velvet disease (also called gold-dust, rust and coral disease) is a fish disease caused by dinoflagellate parasites of the genus "Piscinoodinium", specifically "Amyloodinium" in marine fish, and "Oodinium" in freshwater fish. The disease gives infected organisms a dusty, brownish-gold color. The disease occurs most commonly in tropical fish, and to a lesser extent, marine aquaria.

Lymphocystis is a common viral disease of freshwater and saltwater fish. The viruses that cause this disease belong to the genus Lymphocystivirus of the family Iridoviridae.

Aquarists often come across this virus when their fish are stressed such as when put into a new environment and the virus is able to grow.

The fish starts growing small white pin-prick like growths on their fins or skin and this is often mistaken for Ich/Ick (Ichthyophthirius multifiliis) in the early stages. It soon clumps together to form a cauliflower-like growth on the skin, mouth, fins, and occasional gills. Lesions at the base of the dorsal fin are common among freshwater species of Central American origin, most notably Herichthys carpentis & inside the mouth of Herichthys cyanoguttatus & Geophagus steindachneri. On the tail fin of Koi, Carps, & US native sunfish (Lepomis sp.) On the side flanks of Walleye, Sauger & Flounder. On random head and/or tail areas of common goldfish, and oranda variants. This virus appears to present itself as a lesion(s) at differing locations depending on the species of fish being attacked, often complicating initial diagnosis.

Lymphocystis does show some host-specificity, i.e., each strain (or species) of lymphocystis can infect only its primary host fish, or some additional closely related, fish.

There is no known cure for this virus, though a privately owned fish research & breeding facility near Gainesville, Florida USA has reportedly been able to suppress the virus into remission using the human antiviral "Acyclovir" at the rate of 200 mg per 10 US gallons for 2 days. Otherwise, some aquarists recommend surgery to remove the affected area if it is very serious, followed by an antibiotic bath treatment to prevent a secondary bacterial infection of the open wounds.

Eventually the growths inhibit the fish's ability to swim, breathe or eat, and secondary bacterial infections usually kills the fish.

Usually the best cure is to simply give the fish a stress free life, a weekly bacteria treatment and the virus will slowly subside and the fins will repair themselves. This can take many months. Like most viral infections, even in humans, the first outbreaks are the most serious, whilst the immune system "learns" how to suppress it, the outbreaks become less severe over time assuming the organism survives the initial outbreaks.