Causative agent: Hexamita spp. / Spironucleus spp. (flagellate protozoan); nutritional deficiency and stray voltage also implicated
Hole in the Head disease is a chronic and distressing condition seen regularly in Australian aquariums, particularly among discus, oscar, and angelfish keepers. The condition is named for the pitted erosions that form across the fish's head and along the lateral line — often weeping a yellowish or white mucus. It is believed to be caused by the flagellate parasite Hexamita in combination with nutritional deficiencies (especially vitamins A and C) and the presence of activated carbon in the filter, which may strip essential trace elements from the water. Stray electrical voltage from faulty equipment has also been linked to outbreaks. In Australian reef tanks, tangs and marine angelfish commonly suffer from a similar condition. Treatment involves a course of metronidazole, available from aquarium suppliers and veterinary clinics across Australia, combined with a diet upgrade to include vitamin-enriched and fresh foods. Addressing all environmental factors simultaneously gives the best chance of recovery.
Symptoms
- •Pits or holes forming on the head and along the lateral line
- •white or yellow mucus trails from the pits
- •loss of appetite
- •white stringy faeces
- •emaciation
- •faded colouration
Treatment
- •Metronidazole (Flagyl) as a bath or in food
- •improve diet with vitamin C and HUFA-rich food
- •remove activated carbon
- •check for stray voltage in tank
- •clean water
Australian Medications
- •Metronidazole available via aquarium suppliers and veterinary clinics in Australia
Commonly Affected Fish
- •Cichlids (discus, oscars, angelfish)
- •marine tangs and angelfish are most susceptible
Important Notes
Common in discus keepers. Remove activated carbon from filter during treatment. Multiple environmental factors involved.