Hole in the Head

Complete guide to identification, timeline, and treatment

What is Hole in the Head?

Hole in the Head (HITH), also known as Head and Lateral Line Erosion (HLLE), is a chronic disease most commonly affecting cichlids, discus, and marine fish such as tangs and angelfish. It causes pitting and erosion of the sensory pores around the head and along the lateral line, linked to the parasite Hexamita, nutritional deficiencies, and poor water quality.

Symptoms

Pitting or crater-like holes around the head and eyes
Erosion along the lateral line
White or yellowish mucus trailing from pits
Loss of colour around affected areas
Lethargy and reduced appetite
Weight loss over time

Causes

Hexamita parasite — internal flagellate linked to HITH
Nutritional deficiencies — lack of vitamins A, C, D, and minerals
Poor water quality — high nitrates and dissolved organics
Activated carbon overuse — may leach minerals from water
Chronic stress from overcrowding or aggression

Hole in the Head Life Cycle and Timeline

Week 1
Small pits or discolouration appear around the head or lateral line. Often mistaken for minor injuries at this stage.
Week 2
Pits deepen and multiply. Mucus trails may become visible. Fish may show reduced appetite and colour fading.
Weeks 3–4
Erosion spreads along the lateral line. Lesions become more pronounced. Secondary bacterial infections may develop in open pits.
Month 2+
Without treatment, lesions continue to expand. Chronic cases can lead to permanent scarring even after recovery.

Treatment Protocol

  • Perform large, frequent water changes (30–50%) to reduce nitrates and dissolved organics
  • Remove activated carbon from the filter — it may deplete essential minerals
  • Improve diet with vitamin-enriched foods, fresh vegetables, and varied nutrition
  • Treat with Metronidazole to target the Hexamita parasite — administer in food or water
  • Add vitamin supplements (especially vitamins A, C, D) to the water or food
  • Address any stressors — reduce aggression, improve tank size, and optimise water parameters

Medication Options

  • Metronidazole (Flagyl) — primary treatment for Hexamita; dose in food for best absorption
  • Seachem MetroPlex — convenient metronidazole formulation; mix with Focus for food dosing
  • Seachem Focus — binds medication to food for internal delivery; use with MetroPlex
  • Vitamin C and A supplements — address nutritional deficiencies contributing to HITH
  • Kanaplex — add if secondary bacterial infection is present in open lesions
  • Improve overall diet with high-quality pellets, frozen foods, and fresh vegetables long-term
Important

HITH is a chronic condition that responds slowly to treatment. Improvement may take weeks to months. Even after recovery, scarring may remain. Prevention through excellent water quality, a varied diet, and low nitrates is far more effective than treatment.

Important Disclaimer

The information provided in this guide is for educational purposes only. Always consult with a qualified aquatic veterinarian or fish health specialist before administering any treatments. Proceed with treatments at your own risk. We are not responsible for any adverse outcomes.