Treatment Protocol for Fish Lice (Argulus)
Physically remove visible lice with tweezers. Treat tank with Dimilin or CyroPro for larvae. Salt dips help. Unlike anchor worms, fish lice are mobile and move across the fish's body.
How to Identify This Condition
Look for these symptoms in your fish:
- Visible flat disc-shaped parasites on body
- Red spots at attachment sites
- Flashing and rubbing against objects
- Irritation and stress
Early detection is critical — the sooner you begin treatment, the better the prognosis. Observe your fish daily during routine feeding for any behavioral or physical changes.
Root Causes
Understanding what caused the problem helps you prevent recurrence:
- Argulus crustacean parasite
- Introduced via infected fish or pond water
- Common in outdoor pond fish
Recommended Medications
The following medications are effective against Fish Lice (Argulus):
- Dimilin — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
- CyroPro — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
- Potassium permanganate — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
Always have these medications on hand before you need them. See our quarantine tank guide for proper treatment setup.
Water Quality During Treatment
Maintain pristine water conditions during treatment. Perform 25% daily water changes using Seachem Prime as your water conditioner. Remove activated carbon from your filter during medication (carbon absorbs medications). Increase aeration with an air stone — sick fish need extra oxygen. Monitor ammonia and nitrite daily with your test kit.
Recovery & Quarantine
With proper treatment, most fish recover within 21 days. Continue treatment for the full course even if symptoms resolve early. Reintroduce treated fish to the main tank gradually, and observe for 7 additional days.
Prevention
The best treatment is prevention. Follow these practices to reduce the risk:
- Quarantine new fish especially pond-raised
- Inspect fish before purchase
- Avoid introducing pond water
For a complete prevention strategy, read our quarantine tank guide and maintenance schedule.