Causative agent: Ichthyophthirius multifiliis — a ciliate protozoan parasite
Freshwater Ich, caused by the ciliate protozoan Ichthyophthirius multifiliis, is widely regarded as the most common disease in Australian freshwater aquariums. Recognisable by the distinctive white spots that appear like grains of salt scattered across a fish's fins and body, this disease spreads rapidly in home tanks and can be lethal if not caught early. The parasite has a complex life cycle — it burrows under the fish's skin to feed, drops to the tank floor to reproduce, then releases free-swimming tomites that seek new hosts. Because only the tomite stage is vulnerable to medication, treatment must be maintained across the full cycle of 7–14 days. Raising the water temperature to around 30°C (for tropical species) accelerates the life cycle and makes treatment more effective. In Australia, Aquasonic Ichonex and Aristopet Multicure are widely available and proven treatments. Quarantining new fish for two weeks before adding them to an established tank is the single best prevention strategy.
Symptoms
- •Tiny white salt-like spots on body, fins, and gills
- •fish rubbing/flashing against objects
- •lethargy
- •loss of appetite
- •labored breathing
- •hiding
Treatment
- •Raise water temperature to 30°C for 10 days to speed parasite life cycle
- •aquarium salt (25–40 tsp per 20L)
- •malachite green (avoid with scaleless fish)
- •copper-based treatments
- •formalin baths
Australian Medications
- •Aquasonic Ichonex
- •Aristopet Rapid White Spot Remedy
- •Aristopet Multicure
- •Aquasonic Bactonex (preventative)
Commonly Affected Fish
- •All freshwater fish
- •especially tetras, goldfish, cichlids, angelfish, barbs
Important Notes
Do not use malachite green on scaleless fish such as catfish or loaches. Treat for the full 7–14 day cycle.
