Columnaris

Columnaris, also known as cotton fin rot or saddleback disease, is a bacterial infection affecting freshwater fish. It is caused by the bacterium Flavobacterium columnare. This pathogen is present in most aquariums and ponds, and outbreaks often occur when fish are stressed due to poor water quality, overcrowding, or injury.

Symptoms of columnaris include a white or yellowish patch that appears on the fins, skin, or mouth of the fish. These patches often have a cotton-like appearance and can spread rapidly. In advanced stages, the affected areas may become eroded, leading to fin damage and difficulty swimming. Affected fish may also appear lethargic, lose their appetite, and rub against objects in the tank. The characteristic lesion can sometimes resemble a saddle shape on the fish's back, hence the name saddleback disease.

Columnaris is highly contagious and can spread quickly among fish. Diagnosis is typically made based on the visible symptoms. Treatment involves improving water quality by performing regular water changes and ensuring adequate filtration. Antibacterial medications can be added to the water or food to treat the infection. It is crucial to remove sick fish from a community tank to prevent further spread. Prevention is key and involves maintaining optimal water parameters and minimizing stress on the fish.