Saltwater Aquarium Fish with Lymphocystis

Clownfish with Lymphocystis

Lymphocystis is a virus that may be found in both saltwater and freshwater fish. This virus, which is caused by a member of the iridoviridae family, causes light-colored pimples on the surface of the fish's skin. Fortunately, these bumps seldom cause major health problems and are usually self-limiting. Most clinical indications may be cleared by focusing on better health management, but prevention is crucial. Because this virus spreads through contaminated water, it's critical to use correct quarantine procedures when adding new fish to your tank. However, because fish might be asymptomatic, it's common for them to have this condition even when given sufficient care when new tank occupants are introduced.

What Is Lymphocystis?

Lymphocystis is caused by a Lymphocystivirus, a family of big iridoviruses that causes light-colored nodules on the skin and fins of fish that range in color from white to grey. The nodules are made up of infected cells that grow in size as the virus replicates, finally ceasing replication and bursting the cell. Because the cell is expanded from 50,000 to 100,000 times the size of a typical, healthy cell, bumps appear on the skin.

Iridoviruses can harm freshwater, brackish, and marine fishes and can be found in all aquatic settings. Other iridoviruses may infect invertebrates and amphibians, and they are widespread across the planet.

Symptoms of Lymphocystis in Saltwater Fish

Raised, white to grey nodules on the skin and fins are the most typical indication of lymphocystis. Symptoms of this virus may appear on the fish in your saltwater aquarium in isolated places or clusters. The following symptoms are common:


  • Raised or slightly raised nodules
  • Nodules are white to grey in coloration, can be pigmented on darker colored skin patches
  • Bumps located on the skin and fins
  • Affected areas may be individual spots or coalesce into cluster

The lymphocystis papilloma-like nodules can vary in size and cluster patterns across the fish's body. They are usually focused on the skin and fins, however aquarium owners may observe nodular pigmentation in darker parts of their fish's skin.

Because of its similar appearance, lymphocystis is sometimes confused with white spot disease, however other illnesses such as encysted parasites, epitheliocystis, epitylis, digenean trematodes, and others can also produce identical symptoms. Prior to pursuing any therapy, it is critical to obtain a precise diagnosis from a skilled aquatic veterinarian.

Causes of Lymphocystis

Lymphocystis, like many other aquatic viruses, may spread horizontally throughout a system by infecting water. This virus is found naturally in the environment, and it may even be transmitted to other places by fish living in crowded settings. Poor water quality or the introduction of sick fish to a tank of otherwise healthy fish are the most prevalent causes in aquariums. Lymphocystis is not thought to transfer from parents to offspring. The following are some of the causes:

  • Infected water
  • Improper quarantine
  • Asymptomatic carrier

Lymphocystis has a latent stage in which a fish can carry the virus without showing any symptoms. The virus usually replicates and the fish begins to develop clinical indications as a result of a secondary stress trigger (such as poor husbandry or water quality difficulties). Once a fish has lymphocystis, it can transfer the infection to other fish in the same system.

Diagnosing Lymphocystis in Saltwater Fish

Your aquatic veterinarian will collect a skin sample for microscopic examination to discover the cause of suspicious white to grey lumps on your fish. Some asymptomatic fish may show indicators of the illness in their internal organs that aquarium owners cannot see. To establish whether your fish are contaminated, your veterinarian may take biopsies or do histopathology, electron microscopy, or molecular tests. They may suggest additional testing based on the results. The treatment will be determined by the test findings.

Environmental evaluations, such as water quality testing, may be conducted in addition to hands-on testing to detect any possible stressors. Stressors that aren't always visible to inexperienced aquarium owners might exacerbate Lymphocystis.


Other than supportive care, there is no therapy for lymphocystis in any species. Correctly diagnosing the reason of any lumps on your fish is vital, as is taking intentional efforts to reduce any stresses in your tank. Fish immune function is harmed by stress, which can lead to a lymphocystis epidemic. Asymptomatic carriers may be present in your system but show no clinical indications, making it difficult to detect a virus-positive fish.

Lymphocystis is frequently self-limiting, but supportive care is critical for your fish's recovery. As your fish recovers, try to be patient and give adequate water quality and a balanced food. You can put them in a quarantine system, but if a single fish develops clinical indications, the virus has already spread across your tank. Quarantining the most infected fish in your tank may help restrict the virus's spread and avoid serious symptoms in the rest of the tank's inhabitants.

Prognosis for Fish With Lymphocystis

Lymphocystis does not usually result in death. This virus usually clears up on its own within six weeks, although seriously affected fish are more vulnerable to bacterial, fungal, and parasitic illnesses. Secondary infections can increase mortality rates in lymphocystis-infected fish, thus aquarium owners should always provide supportive care to their animals during outbreaks.

How to Prevent Lymphocystis

Aquarium owners cannot always prevent lymphocystis, but there are a few methods that may decrease the likelihood of this virus spreading to your tank:

Quarantine New Fish

The easiest way to avoid getting lymphocystis is to quarantine any new fish, including invertebrates, for 30 to 60 days. If your fish is a carrier, the stress of capture, transfer, and introduction to a new system is typically enough to start a lymphocystis outbreak. This frequently results in apparent signs that aquarium owners may recognize, indicating that the fish should be carefully diagnosed by a veterinarian before any action is done.

However, due to the virus's latency, quarantine does not guarantee that lymphocystis will not spread. If there is any possibility that aquarium equipment has come into touch with this virus, it should be disinfected. Asymptomatic carriers can frequently escape quarantine and infect healthy fish in your aquarium. Fortunately, because this sickness is largely an aesthetic issue, most fish owners shouldn't be too concerned about it. Most outbreaks may be resolved in a few weeks with good supportive treatment.

Keep Water Conditions Optimal

Aquarium owners may assist limit the probability of their fish getting lymphocystis by maintaining the tank's water parameters appropriate, in addition to carefully quarantining all incoming fish. Because stress can cause outbreaks of this virus, it's crucial to handle fish carefully and minimize overpopulation. Any circumstances that might cause physical stress in the fish should be avoided as much as possible.

Is Lymphocystis Contagious to Humans?

Other iridoviruses can infect people, but the fish forms are not zoonotic, meaning they cannot transfer to humans. There are bacteria that may transmit to humans, such as mycobacteria, but viruses are less zoonotic.