Ammonia spike or low oxygen drives fish to attempt escape. Test water + immediate water change.
Bullied fish jump to escape. Solution: separate aggressor, add hiding spots, rearrange decor.
Firefish, gobies, killifish, hatchetfish, knife-fish, arowana - ALL jump. Always have a tight-fitting lid + screened openings.
Fish without hiding spots feel exposed + stressed. Add plants + caves.
Sudden lights-on causes startled jumps. Use a sunrise/sunset ramp on programmable LEDs.
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 full disease database if illness is suspected.
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