External Parasites (Flukes, Anchor Worm, Fish Lice)
Includes skin and gill flukes, anchor worms, and fish lice (Argulus). Fish may scratch against objects (flashing) and produce excess mucus. Often introduced with new fish or live food.
Check these symptoms in your tankSymptoms of External Parasites (Flukes, Anchor Worm, Fish Lice)
- Scratching against objects (flashing)
- Spinning or erratic movement
- Rapid gill movement / labored breathing
- Excess mucus / slime coat
- Fins clamped against body
- Lethargic / hiding more than usual
How to treat External Parasites (Flukes, Anchor Worm, Fish Lice)
- Identify the specific parasite if possible
- Praziquantel (PraziPro) for flukes
- API General Cure for general parasite treatment
- Remove visible parasites (anchor worm, lice) with tweezers
- Treat the whole tank, since parasites spread quickly
How to prevent it
- Quarantine all new fish for 4 weeks
- Quarantine or freeze live food before feeding
- Rinse new plants and quarantine them before adding
- Maintain good water quality to support the immune system
Conditions with similar symptoms
The most common aquarium disease. Caused by the parasite Ichthyophthirius multifiliis. Looks like salt grains on the fish's body and fins.
Saltwater equivalent of freshwater ich. Caused by Cryptocaryon irritans. More difficult to treat than freshwater ich.
Caused by a dinoflagellate parasite. Appears as a fine gold or rust dust on the fish. Highly contagious and fast-moving, often fatal if not treated immediately.
Not sure? Use the symptom checker
Many fish diseases look alike. Pick the symptoms you see in the free fish disease checker to compare likely causes, or scan a test strip to rule out a water problem first.