Columnaris

Symptoms

Early recognition is the key to a good outcome, so inspect your fish daily at feeding time. White/grey cottony patches, 'saddleback' lesions across the back, frayed mouth and fins, rapid breathing. If you notice several of these signs together, act promptly rather than waiting.

Causes

A bacterium that thrives in warm, dirty, low-oxygen water and attacks stressed or injured fish. In almost all cases 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

Lower the temperature slightly (warmth accelerates it), improve oxygenation and water quality, and treat with an antibacterial effective against gram-negative bacteria. Acts quickly so treat immediately.

Throughout treatment, increase aeration, remove activated carbon from the filter (it absorbs medication), complete the full course even after symptoms fade, and keep the water immaculate with regular changes. Always follow the medication's dosing instructions and dose for the tank's true water volume.

Prevention

Avoid overcrowding and warm stagnant water; keep oxygen high and water clean. The golden rules are simple: quarantine every new fish for 2-4 weeks, never overstock or overfeed, avoid sudden temperature or chemistry swings, and perform regular partial water changes. A stable, clean, low-stress aquarium prevents the overwhelming majority of disease outbreaks.

FAQ

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