Bacterial Fin Rot: symptoms, treatment, prevention
Bacterial Fin Rot is a common opportunistic infection of fin margins by mixed Gram-negative bacteria, usually secondary to injury or poor water quality.
Overview
Bacterial Fin Rot is caused by a mixed Gram-negative flora (Aeromonas, Pseudomonas, Flavobacterium spp.). It usually appears as a secondary infection after fin-nipping injuries, poor water quality or stress, and is one of the most common bacterial diseases in home aquaria.
Symptoms
- Frayed and ragged fin edges
- White rim along the fin margin
- Progressive fin loss
- Redness at the fin base
- Lethargy in advanced cases
- Secondary fungal growth on damaged tissue
Causes
Triggers include fin-nipping tankmates, sharp decor edges, missed water changes, elevated ammonia or nitrite, and any chronic stressor that suppresses the slime coat.
Diagnosis
Receding fin edges with a pale or red rim are characteristic and easy to recognise. Differentiate from mechanical fin damage (clean edges without redness) and from columnaris (gray-white film on the body, not just fins).
Treatment
Mild cases respond to water-quality correction alone; only advanced cases with body involvement need antibiotics.
Quarantine
For mild fin damage, treat in the main tank after addressing water quality. For advanced cases, move the fish to a hospital tank for an antibiotic course.
Medication
- Perform a 50 % water change, vacuum the substrate, and add aquarium salt at about 1 g per litre for 7 days; mild cases usually resolve without antibiotics.
- For advanced cases with body involvement, use a nitrofuran derivative or kanamycin sulfate in quarantine for 7-10 days.
Recovery
Fins regrow over weeks once the bacterial process is controlled. Maintain pristine water quality and remove the original aggressor or sharp object to prevent recurrence.
Prevention
- Maintain pristine water quality
- Avoid fin-nipping tankmates
- Remove sharp decor edges
- Feed a balanced diet for immune health