What are the symptoms of Gill Flukes?

Visibly rapid gill movement with the fish hanging at the surface or in the filter flow; Excess mucus on the gills, pale gill colour and, in severe cases, frayed gill filaments; One gill cover stays flared open and does not close, or the covers turn outward; Localised redness, frequent flashing, poor appetite and gradual weight loss. It usually starts with: Parasites or eggs introduced with unquarantined fish; Overcrowding and deteriorating water quality lowering resistance; Large temperature swings triggering hatching and repeated infections.

How do you treat Gill Flukes?

In order: 1. Isolate affected fish (Move affected fish into a hospital tank with dedicated tools. Fluke eggs tolerate medication well, so treat the display tank in parallel or leave it fallow long enough.) 2. Change water and boost aeration (Change 30% of the water with matched temperature and clear the debris. With damaged gills, dissolved oxygen is the first priority, so run the air pump hard.) 3. Praziquantel bath (Bath at 2-5 mg/L, repeating every 5-7 days for 2-3 rounds to kill newly hatched larvae; a single dose cannot kill the eggs, which is why the course must be repeated.) 4. Formalin if required (Hospital tank only, as a short bath at the label dose, watching the fish the whole time; pull it out immediately if it rolls over or stops breathing. Formalin is lethal to corals, shrimp, snails and other invertebrates.) 5. Re-check gill condition after treatment (Watch for a week after treatment to confirm breathing has normalised and flashing has stopped; if not, run another round of praziquantel.)

What medication treats Gill Flukes?

Praziquantel: Hospital tank bath at 2-5 mg/L, repeated every 5-7 days for 2-3 rounds, or given in food at the label dose. It is relatively gentle, but the repeated dosing is what covers the eggs.; Formalin: Hospital tank only, as a timed bath at the label dose, with the fish under constant watch. It is lethal to corals, shrimp, snails and live rock life and must never enter the display tank; it also harms plants and the biofilter.

G-04 / 03Freshwater

Gill Flukes鳃吸虫

Moderate. The prognosis is good with prompt treatment, but the eggs make repeated dosing mandatory; untreated, the fish decline slowly from gill damage and oxygen starvation.

Illustration to come

G-04 / 03 · Gill Flukes

SpecificationsDisease atlas

Cause: Parasite
Severity: Moderate
Contagion: Highly contagious
Corals / inverts: Not safe
Also known as: Dactylogyrus / Gyrodactylus、Gill worms

Symptoms

Visibly rapid gill movement with the fish hanging at the surface or in the filter flow
Excess mucus on the gills, pale gill colour and, in severe cases, frayed gill filaments
One gill cover stays flared open and does not close, or the covers turn outward
Localised redness, frequent flashing, poor appetite and gradual weight loss

Typical triggers

— Parasites or eggs introduced with unquarantined fish
— Overcrowding and deteriorating water quality lowering resistance
— Large temperature swings triggering hatching and repeated infections

Treatment, in order

1 · IsolateIsolate affected fishMove affected fish into a hospital tank with dedicated tools. Fluke eggs tolerate medication well, so treat the display tank in parallel or leave it fallow long enough.
2 · Water changeChange water and boost aerationChange 30% of the water with matched temperature and clear the debris. With damaged gills, dissolved oxygen is the first priority, so run the air pump hard.
3 · MedicationPraziquantel bathBath at 2-5 mg/L, repeating every 5-7 days for 2-3 rounds to kill newly hatched larvae; a single dose cannot kill the eggs, which is why the course must be repeated.
4 · MedicationFormalin if requiredHospital tank only, as a short bath at the label dose, watching the fish the whole time; pull it out immediately if it rolls over or stops breathing. Formalin is lethal to corals, shrimp, snails and other invertebrates.
5 · ObserveRe-check gill condition after treatmentWatch for a week after treatment to confirm breathing has normalised and flashing has stopped; if not, run another round of praziquantel.

The standard treatment uses copper or formalin, which is lethal to corals, shrimp, snails and everything on live rock. Treat in a quarantine tank only, and leave the display tank fallow for the full period above before returning the fish.

Medications and cautions

Praziquantel: Hospital tank bath at 2-5 mg/L, repeated every 5-7 days for 2-3 rounds, or given in food at the label dose. It is relatively gentle, but the repeated dosing is what covers the eggs.
Formalin: Hospital tank only, as a timed bath at the label dose, with the fish under constant watch. It is lethal to corals, shrimp, snails and live rock life and must never enter the display tank; it also harms plants and the biofilter.

Prevention

Quarantine new fish for 2-4 weeks and run one deworming round during quarantine
Keep stocking density and organic load under control
Hold the temperature gap within 1 °C at water changes to reduce stress-triggered hatching

Frequently asked questions

What are the symptoms of Gill Flukes?: Visibly rapid gill movement with the fish hanging at the surface or in the filter flow; Excess mucus on the gills, pale gill colour and, in severe cases, frayed gill filaments; One gill cover stays flared open and does not close, or the covers turn outward; Localised redness, frequent flashing, poor appetite and gradual weight loss. It usually starts with: Parasites or eggs introduced with unquarantined fish; Overcrowding and deteriorating water quality lowering resistance; Large temperature swings triggering hatching and repeated infections.
How do you treat Gill Flukes?: In order: 1. Isolate affected fish (Move affected fish into a hospital tank with dedicated tools. Fluke eggs tolerate medication well, so treat the display tank in parallel or leave it fallow long enough.) 2. Change water and boost aeration (Change 30% of the water with matched temperature and clear the debris. With damaged gills, dissolved oxygen is the first priority, so run the air pump hard.) 3. Praziquantel bath (Bath at 2-5 mg/L, repeating every 5-7 days for 2-3 rounds to kill newly hatched larvae; a single dose cannot kill the eggs, which is why the course must be repeated.) 4. Formalin if required (Hospital tank only, as a short bath at the label dose, watching the fish the whole time; pull it out immediately if it rolls over or stops breathing. Formalin is lethal to corals, shrimp, snails and other invertebrates.) 5. Re-check gill condition after treatment (Watch for a week after treatment to confirm breathing has normalised and flashing has stopped; if not, run another round of praziquantel.)
Is Gill Flukes contagious, and how urgent is it?: Contagion: highly contagious. Severity: moderate. Cause: parasite. Moderate. The prognosis is good with prompt treatment, but the eggs make repeated dosing mandatory; untreated, the fish decline slowly from gill damage and oxygen starvation.
What medication treats Gill Flukes?: Praziquantel: Hospital tank bath at 2-5 mg/L, repeated every 5-7 days for 2-3 rounds, or given in food at the label dose. It is relatively gentle, but the repeated dosing is what covers the eggs.; Formalin: Hospital tank only, as a timed bath at the label dose, with the fish under constant watch. It is lethal to corals, shrimp, snails and live rock life and must never enter the display tank; it also harms plants and the biofilter.
Is the treatment for Gill Flukes safe for corals and inverts?: No. The standard treatment (copper or formalin based) is lethal to corals, shrimp, snails and everything on live rock. Treat in a quarantine tank only, and leave the display tank fallow for the full period given above.