Goldfish Flashing and Bottom-Bashing After New Fish Added: Quarantine Failure

10-year-old goldfish start flashing (rubbing on gravel) after new fish added months ago; 2 new fish died. Owner added air pump, asks if it’s the cause.

Classic New-Fish Disease Introduction

New fish likely carried parasites (flukes, ich, trichodina) or bacteria. Without 1–2 week quarantine, they infected the established population. Air pump is beneficial, not harmful.

Diagnosis & Treatment

1. Check for raised scales (pineconing) → dropsy/bacterial.
2. Look for white spots (salt-grain) → ich.
3. Flashing + no spots → flukes or external parasites.
4. Microscope scrape confirms.
5. Treat specifically: Praziquantel for flukes; malachite/formalin for ich; antibiotics for bacterial ulcers.

Lesson

Always quarantine new arrivals. A simple 10-gallon tank with filter and heater for 14 days prevents 90% of such outbreaks.