Infectious stomatitis in moray eels
Infectious stomatitis is inflammation of the mouth affecting moray eels in captivity, most often in reef aquariums or display tanks. It appears as lesions on the jaws and inside the mouth, sometimes with pus or whitish deposits. This is a c...
What is it?
Infectious stomatitis is inflammation of the mouth affecting moray eels in captivity, most often in reef aquariums or display tanks. It appears as lesions on the jaws and inside the mouth, sometimes with pus or whitish deposits. This is a common condition in stressed moray eels or those injured during capture or handling.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Early signs are often subtle: the moray eats less well or refuses food. Swelling may be noticed around the mouth or jaws, sometimes one-sided. Red areas, small wounds, or whitish or yellowish deposits appear on the gums or lips. The animal may drool excessively or show stringy saliva. In advanced cases, deeper ulcers develop, sometimes with an unpleasant smell. The moray becomes sluggish, stays hidden more than usual, or swims abnormally near the bottom or décor. It may also rub its mouth against rocks or sand, a sign of discomfort.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Infectious stomatitis is usually caused by opportunistic bacteria, particularly certain Vibrio species or other marine bacteria naturally present in water. These bacteria take advantage of wounds, tooth damage, or a weakened immune system to colonize the oral mucosa. Injuries can occur from fighting with others of the same species, bumping into décor, or stressful handling during transport or capture.
Poor water quality with high levels of ammonia, nitrites, or nitrates promotes the disease. Chronic stress from overcrowding, aggressive tankmates, or repeated transport weakens the animal's natural defenses. Inappropriate diet or insufficient quantity and quality of food may also play a role. Recently wild-caught moray eels are at particular risk because of transport stress and adjustment to the new environment.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The aquatic animal veterinarian performs a visual examination of the mouth and assesses the animal's general condition. A swab of the lesions may be taken to identify the bacteria through microbiological culture. Water quality analysis of the tank is routine, as environmental factors often underlie the diagnosis.
Treatment
Treatment is based on antibiotics chosen according to the bacteria identified, given by mouth mixed into food or by injection depending on the case. Local cleaning of lesions may be performed by the veterinarian. Prompt improvement of water quality and stress reduction are essential parts of care.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Maintaining excellent water quality is the most important preventive measure: effective filtration, regular monitoring of water parameters, and appropriate water changes. Stress should be minimized by providing sufficient hiding places and space appropriate to the animal's size. Quarantining new arrivals allows problems to be detected before introduction into the main tank. Gentle and infrequent handling reduces the risk of mouth injuries. A varied, high-quality diet supports the immune system.
Possible complications
Without treatment, the infection may spread to deep tissues of the jaw, causing deformation or tooth loss. The weakened animal eats less and less, leading to progressive weight loss. In severe cases, sepsis can develop when bacteria spread throughout the body, putting the animal's life at risk.
When to see a veterinarian
The moray eel has refused food for several days.
Swelling or lesions appear around the mouth.
The animal remains lethargic or hidden constantly.
Unusual odor or suspicious deposits are visible in the mouth.
Swimming becomes abnormal or the animal appears in distress.
Prognosis
The prognosis is good if the disease is caught early and water quality is corrected alongside antibiotic treatment. Delayed treatment or infection already spread to deep tissues worsens the prognosis, with a risk of death if sepsis develops.
Frequently asked questions
Is infectious stomatitis in moray eels contagious to other fish?
The bacteria responsible are often already present in the water. The risk of transmission depends mainly on the water quality and the stress levels of other pool occupants rather than on direct contact.
Can you treat a sick moray eel without a specialized veterinarian?
It is strongly advised against administering an antibiotic without professional guidance. A poor choice or misuse can worsen the animal's condition and promote bacterial resistance.
How do you know if your aquarium water is the problem?
Only a water parameter analysis carried out by a professional or with reliable test equipment can confirm an imbalance that could favor disease.
Can a healed moray eel suffer a relapse?
Yes, if stress factors or poor water quality are not permanently corrected, relapses are possible.
References
AVMA — American Veterinary Medical Association
Content reviewed by the TunisieVet editorial team · Updated 23 August 2026
Comments (0)
No comments yet.
AT A GLANCE
Need a veterinarian?
Find a practitioner near you on TunisieVet, with their specialities, hours and contact details.
Find a veterinarianCategories
Affected species
This information is provided for educational purposes only and is not a substitute for a veterinary consultation. If you have any concerns about your animal's health, consult a veterinarian.
Thinking of welcoming a pet? Dogs and cats are waiting for a family in Tunisia, and adoption is completely free.
Adoption listingsTo discover
Related diseases and linked Animalia content.
White spot disease in moray eels
Parasitic
Bacterial Skin Infection in Moray Eels
animalia::front.disease_types.bactérienne
Gastrointestinal parasitism in moray eels (roundworms)
Parasitic
