Achlya Infection: causes, symptoms and treatment
Achlya Infection (Achlya spp.) — etiology, symptoms, diagnosis, active-substance medication, recovery and prevention; mortality without treatment: low.
Overview
Closely related oomycete to Saprolegnia, less aggressive but produces similar cottony patches on skin and eggs. Treatment is identical. Causative agent: Achlya spp.. Transmission: water. Incubation: 2-10 days. Reported mortality without treatment: low.
Symptoms
- white cottony tufts on body and fins
- grey film
- secondary fin damage
- egg infection in breeding setups
- lethargy
Causes
Outbreaks are typically triggered by chronic stress, poor water quality, temperature swings, overcrowding, or the introduction of unquarantined fish. The pathogen spreads via free-swimming or waterborne stages in shared water. The agent is not directly contagious between cohabitants, but it shares risk factors with the rest of the stock.
Diagnosis
Diagnosis is based on clinical signs (cottony or fuzzy growths on skin, fins, or gills) and microscopy of a fresh scrape, which reveals hyphae of Achlya spp.. Most cases are secondary to injury or pre-existing damage, so search for the underlying trigger.
Treatment
Effective treatment requires isolating affected fish in a quarantine tank, identifying the pathogen, administering the appropriate active substance at the correct dose and duration, and supporting recovery with stable water parameters and nutrition.
Step 1: Quarantine
Set up a bare-bottom quarantine tank with a mature sponge filter, heater, and aeration. Match temperature and pH to the display tank, and acclimate fish slowly. A bare bottom simplifies daily siphoning and prevents medication from being absorbed by substrate.
Step 2: Medication
- Salt + methylene blue. Same as Saprolegnia: salt 1 tsp/gal + methylene blue dip 3 ppm 30 min. (duration: 5-7 days)
Step 3: Recovery
After medication, perform a 30-50% water change and run fresh activated carbon for 24-48 hours to remove residues. Continue feeding a high-quality, varied diet with vitamins and immunostimulants. Reintroduce fish to the display tank only after at least one week without recurrence of symptoms.
Prevention
- good water quality
- remove dead organic matter
- avoid handling injuries
- remove dead eggs