Hexamitosis (Hole-in-the-Head Disease) in Cichlids: Causes and Treatment
Small skin erosions that gradually deepen on the head or along the lateral line of certain cichlids, particularly large South American cichlids and discus, are known as hole-in-the-head disease or lateral line erosion. A study by Paull and Matthews, published in 2001 in the journal Diseases of Aquatic Organisms, identified the flagellate Spironucleus vortens as a possible cause of this syndrome in cichlids, while noting that other nutritional and environmental factors likely play a role as well (study on Google Scholar). Find our other health pointers in the care and grooming section.
Which cichlids are most affected?
Large South American cichlids (oscars, severums) and discus are among the species most often affected, while African cichlids from Lake Malawi seem less prone to it under typical aquarium conditions. Our article on the African cichlid aquarium covers the specific needs of that group, quite different from the South American cichlids most associated with hexamitosis.
What role do diet and water quality play?
A poor or narrow diet and chronically elevated nitrates are frequently associated with the onset or worsening of the syndrome, even though the exact causal link remains debated in the scientific literature. Regular parameter checks, via water tests, and a varied diet remain the first levers to pull.
What treatment should you consider?
An antiparasitic targeting flagellates, combined with a clear improvement in water quality and diet, gives the best results. Isolating the affected fish in a hospital quarantine tank makes treatment and monitoring easier without stressing the rest of the group.
Can this syndrome be prevented?
A stable, uncrowded tank with regular water changes and a varied diet, including fibre-rich foods for herbivorous species, remains the best known prevention, even without a single clearly established cause.
- Small erosions on the head or lateral line, slow progression.
- South American cichlids and discus more affected than African species.
- Diet and water quality as major associated factors.
- Antiparasitic treatment + environmental improvement together.
Frequently asked questions
Is hexamitosis contagious between fish?
The flagellate involved can be present in several fish in the tank without necessarily triggering visible symptoms in all of them; individual stress appears to play a decisive role.
Can the erosions heal completely?
Yes, in many cases, once the cause is treated and the environment improved, the skin can gradually heal over several weeks.
Should the whole diet be changed on suspicion?
Diversifying the diet is recommended, especially for species with herbivorous tendencies, rather than an abrupt overhaul that would add extra stress.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.