Chilodonelliasis: symptoms, treatment, prevention
Chilodonella piscicola is a heart-shaped ciliate parasite of skin and gills, typically active in cool water below 20 °C.
Overview
Chilodonelliasis is caused by Chilodonella piscicola, a heart-shaped ciliate that attacks skin and gills. It is most often a cool-water disease, with outbreaks below about 20 °C; it causes excess mucus production and severe respiratory distress and can be fatal if untreated.
Symptoms
- Bluish-grey mucus film over the body
- Clamped fins
- Flashing against substrate
- Rapid breathing
- Lethargy
- Frayed fins
Causes
Introduction with new fish or contaminated water; outbreaks are triggered by low temperatures, overcrowding and poor water quality that allow the parasite to multiply.
Diagnosis
A bluish-grey mucus film over the body in cool-water conditions is characteristic. Confirmation is by microscopy of a skin or gill scrape showing the characteristic heart-shaped ciliate, which distinguishes Chilodonella from Trichodina (disc with denticles) and Ich (large encysted trophonts).
Treatment
Combine an immediate environmental correction (raise temperature where species tolerates, improve water quality) with a parasiticide bath or dip.
Quarantine
Move affected fish to a hospital tank with stable warm water (above 22 °C where species tolerates) and strong aeration. Run baths or dips outside the display so medications do not affect plants or invertebrates.
Medication
- Aquarium salt (NaCl) at about 1 g per litre in the hospital tank for 5-7 days alongside increased aeration.
- Formalin bath at 25 ppm for 30-45 minutes with strong aeration; repeat after 3 days if symptoms persist.
- Potassium permanganate short bath as an alternative parasiticidal dip, dosed per veterinary protocol.
Recovery
Resume normal feeding and large water changes after the parasite is cleared. Address the underlying cool temperature or overcrowding that allowed the outbreak.
Prevention
- Maintain temperature above 22 °C where species tolerates
- Quarantine new fish
- Avoid overcrowding
- Maintain consistently good water quality