Parasites: when to treat (and how to avoid random “dumping”)

Step 0: water first (always)

• Test ammonia/nitrite, pH, KH, temperature.
• If ammonia/nitrite are present: do water changes + detox + aeration first.
• Only treat parasites when water is stable enough to handle treatment.

Decision tree (simple)

1. One fish only, new injury, or localized issue → consider injury/stress first.
2. Multiple fish flashing/rubbing, clamped fins, irritability → parasites more likely.
3. Gasping / heavy breathing → could be gills: parasites, ammonia/nitrite, CO₂, irritation.
4. If you can scope: do it. If you can’t: use the structured plan below.

The “Shotgun (best-effort)” plan — with guardrails

This is designed for the 99% who cannot run a proper quarantine or microscope workflow. It’s still safer than random meds because it follows a sequence and avoids common mistakes.

• Do not combine meds unless you know they’re compatible.
• Keep aeration strong during treatments.
• Don’t treat if fish are already in severe distress from water quality—fix water first.
• Follow label directions exactly and do the required re-doses (life cycle matters).

Shotgun sequence (recommended order)

1. Target protozoans first (common “flashing” causes).
2. Then target flukes (very common and often missed).
3. Then reassess: if symptoms improve, stop. If not, re-check water and consider microscopy or expert help.

When NOT to shotgun

• Ammonia or nitrite present (treat water first)
• Fish rolling, severe respiratory distress (stabilize water + aeration immediately)
• Recent large pH swings / low KH (stabilize KH first)
• Water is very cold and the chosen treatment isn’t appropriate at that temp

What “success” looks like

• Reduced flashing within a few days (not always immediate).
• Normal swimming, normal appetite returning, less surface irritation behavior.
• If nothing changes: stop stacking meds and re-check water + consider scoping.