Symptoms
Ulcers / red sores
Goal: identify the most likely causes and take safe, high-impact steps first.
Check these first (in order)
- Ammonia / nitrite (fix water first)
- pH + KH (stability matters for healing)
- Temperature (healing slows in cold water)
- Number of fish affected (one fish vs many)
- Recent handling/injury (spawning, netting, predators)
Common causes
- Underlying stressor — Often water quality, temperature swings, or overcrowding.
- Bacterial involvement — Opportunistic bacteria take hold when fish are stressed.
- Parasite irritation — Parasites can create entry points for infection.
- Physical injury — Netting, spawning, predators, sharp edges.
Safe next steps
- If ammonia/nitrite: do a water change, boost aeration, and stabilize.
- Stabilize KH/pH and avoid large daily swings.
- If symptoms persist and water is stable: consider a parasite plan (microscope is best).