Quick referenceHole In The Head (HITH) and Head + Lateral Line Erosion (HLLE) are linked conditions causing pitting + erosion. Treat with metronidazole + improved diet (omega-3, garlic, vitamins).
Symptoms
Hole in head
Pits + erosion along lateral line
Color fade
Refusing food
Sunken eyes
Lethargy
Cause
Multifactorial: 1) Spironucleus + Hexamita protozoan parasites (especially in cichlids, discus). 2) Nutritional deficiency (vitamin C, vitamin A, omega-3). 3) Poor water quality (chronic high nitrate, activated carbon dust irritation in saltwater). Often a combination.
Treatment options
Metronidazole. Targets Spironucleus + Hexamita. 250mg per 10 gal weekly for 3-4 doses. Soak pellets in metro for 30 min before feeding to deliver internally.
Stop carbon use (saltwater). Some studies link granulated activated carbon (GAC) to HLLE in tangs. Try ceasing GAC for 6-8 weeks.
Improve water quality. Reduce nitrate to under 10 ppm reef / under 30 ppm freshwater. Increase water-change frequency.
Always treat in a separate quarantine or hospital tank. Most medications are toxic to coral, invertebrates, and live rock biology. Consult an aquatic veterinarian for valuable fish.
Prevention
Varied high-quality diet (not just one pellet brand). Avoid chronic high nitrate. Use less GAC in saltwater tang systems. Quarantine new cichlids.
Fatality + outcome
Slow but progressive. Untreated severe HITH causes permanent disfigurement + secondary infections; mild cases reverse with treatment.