Torn, ragged, or disappearing fins
This looks like: mechanical damage from aggression OR bacterial fin rot — sometimes both once bacteria move in
Why this happens
Sharp clean splits often mean aggression or décor. Black-edge melt with red spreading often rots. Poor water worsens every version.
How sure are we? Pattern read — photo at lights-out helps bullying truth.
What to do right now
- Test ammonia and nitrite — rot thrives in dirty margins.
- Rearrange or add visual breaks; watch after dark.
- Salt only if species tolerate — research first, measure grams.
- Dose appropriate antibacterial only if rot advances after water is clean.
- Never tear extra fin with net rush — slow net, calm handling.
What not to do
- Don’t leave long-finned fish with known nippers without exits.
If that doesn’t fix it
If body ulcers appear, jump to bacterial ulcer path.
Catch this earlier next time — log your water parameters in App-aquatic. Free forever.