Chilodonella

Symptoms

Spotting illness early gives the best chance of a cure, so check your fish daily at feeding time. A whitish, cloudy slime coating, flashing, clamped fins, gasping and lethargy. Like Costia, it is invisible without a microscope. If you see several of these signs together, act promptly rather than waiting.

Causes

A protozoan skin and gill parasite that explodes in cool, dirty, overcrowded water and on stressed fish. In nearly every case the underlying trigger is stress, poor water quality, or the introduction of an infected fish - all of which weaken a fish's natural defences.

Treatment

Improve water quality, raise temperature if the species tolerates it, and treat with an anti-protozoan parasite medication for the full course. Treat the entire tank.

While treating, increase aeration, remove activated carbon from the filter (it absorbs medication), finish the full course even after the fish looks better, and keep the water immaculate with regular changes. Always dose for the tank's true water volume and follow the product instructions.

Prevention

Avoid overcrowding and chilling, keep water clean, and quarantine new arrivals. The golden rules are simple: quarantine every new fish for 2-4 weeks, never overstock or overfeed, avoid sudden temperature or chemistry swings, and do regular partial water changes. A stable, clean, low-stress aquarium prevents the large majority of disease.

FAQ

This information is general guidance, not veterinary advice. Consult an aquatic vet for serious cases.