Hole-in-the-Head Disease (Hexamita) in Discus and Cichlids: Treatment Guide

Hole-in-the-head disease shows up as small pits or craters on a fish’s head and lateral line, and it is most often linked to the parasite Hexamita combined with poor water quality or nutrition. Discus, oscars, and other cichlids are especially prone. The standard hobbyist treatment is metronidazole — dosed in the water or via medicated food — alongside aggressive water-quality and diet improvements. Treated early, the pits heal and scar over.

What are the symptoms?

• Small pits or holes on the head, often starting above the eyes
• Erosion along the lateral line (head-and-lateral-line erosion, or HLLE)
• White, stringy feces — a classic sign of an internal hexamita load
• Loss of appetite, pale color, and hiding behavior

What causes hole-in-the-head disease?

Most cases involve three factors stacking up: the Hexamita parasite (present at low levels in many healthy fish), chronic stress from water quality (high nitrates are repeatedly implicated by hobbyists and aquaculture references), and nutritional gaps — particularly vitamin and mineral deficiencies in fish fed a narrow diet. When stress suppresses the immune system, the parasite multiplies and the characteristic pits appear.

How do you treat it?

1. Get nitrates down. Large, frequent water changes (25–50%), substrate vacuuming, and reduced feeding. Target under 20 ppm nitrate.
2. Treat with metronidazole. The hobby standard is metronidazole such as Fish Zole 250mg (or Fish Zole 500mg for larger systems). Typical label directions dose one capsule per 10 gallons every 24 hours for 5–10 days with partial water changes between doses — follow your bottle’s label. Because hexamita is internal, fish that are still eating respond fastest.
3. Upgrade the diet. Vary foods and add vitamin-rich options; many keepers soak food in a liquid vitamin supplement during recovery.
4. Reduce stress. Stable temperature, good oxygenation, and calm tank mates while the fish heals.

Will the holes heal?

Yes — in most treated fish the pits stop expanding within one to two weeks and gradually fill with scar tissue over the following month. Deep, long-standing erosion may leave visible scarring but is rarely dangerous once the underlying cause is fixed. Recovery stalls almost always trace back to nitrates creeping up again or diet slipping back to a single food.