How to quarantine fish
9 min read
Quarantine is the single best insurance policy for your tank. One 4-week QT prevents months of disease nightmares.
Why QT?
Marine ich (Cryptocaryon) and velvet (Amyloodinium) can wipe out a display in days. Even healthy-looking fish carry parasites. A 30-day QT with proactive treatment breaks the parasite life cycle before fish enter your main system.
Build a QT
Bare-bottom 10–20 gallon tank, heater, sponge filter (pre-seeded if possible), PVC elbows for hiding, a small light, and a tank lid. No substrate, no rock — both bind copper.
Saltwater treatment protocol
Option A (copper): Chelated copper (Copper Power or Coppersafe) at 1.75–2.5 ppm for 30 days. Test daily with a Hanna copper checker. Option B (tank transfer method): Move fish to fresh saltwater every 72 hours for 4 transfers — kills ich without medication. Always treat for flukes with prazipro on day 1 and day 7 either way.
Freshwater QT
Less intense — 2 weeks of observation usually suffices. Treat preventatively with a praziquantel + metronidazole combo if any flashing or scratching is observed. Watch for ich (visible white spots).
When can they go in the display?
After 30 days with no symptoms, eating well, and full color. Acclimate slowly — drip for 60 minutes — and lights off for the first 24 hours in the new tank.