Stage 1: Edges Fray
The fin margin becomes ragged, slightly white or red. Fish behavior is normal. Cause is almost always poor water quality — ammonia or nitrite above 0.
Treatment: 50% water change daily for a week. Add 1 tsp aquarium salt per 10L. Re-test parameters.
Stage 2: Decay Spreads
Fin tissue recedes 3-5mm. Veins become visible. Fish may clamp fins or rub on decor. Secondary fungal growth (white fluff) may appear.
Treatment: Add methylene blue 2mg/L. Continue water changes. Melafix boosts regeneration.
Stage 3: Body Approach
Fin reaches the body — blood streaks appear in remaining tissue. Fish becomes lethargic, refuses food. Septicemia risk is imminent.
Treatment: Kanamycin or furan-2 dosed per label for 7-10 days. Salt bath 30 min daily at 3% saline.
Stage 4: Body Ulcer
Body tissue starts eroding where fin attached. At this point mortality is 50%+. Aggressive antibiotic (levofloxacin or injectable ceftazidime) is needed.
Prevention is the only reliable solution — weekly 50% water changes, pristine filtration, no overstocking.