Ammonia, nitrite, or pH crash causes immediate fin clamping. Test + 50% water change.
Ich, fin rot, fungus often start with clamped fins before visible symptoms. Watch for spots in 24-48 hours.
Bullying + chasing causes chronic clamping. Watch tank dynamics + remove aggressor.
Recently added fish clamp fins for 1-3 days during acclimation. Normal if appetite returns.
Test water first - many "behavior" issues are actually water-quality problems. Use the water parameter checker to score your test results, the disease symptom matcher if you observe physical signs, or the general diagnoser to narrow further. Browse the disease database if illness is suspected.
Browse all behavior troubleshooting articles.