A quarantine tank (QT) is one of the most valuable investments in the hobby, second only to the display tank itself.
Why it matters:
Disease prevention — Marine ich, velvet (Amyloodinium), and flukes are extremely common in fish store systems. A new fish can look perfectly healthy and still be carrying parasites.
Reef tanks can't be medicated — Copper, formalin, and most effective fish medications will kill corals, invertebrates, and your biological filtration. If disease gets into your display tank, your only option is removing every fish and running it fallow for 76+ days.
It protects your existing fish — One infected fish can wipe out an entire established tank in days, especially with velvet.
What a basic QT needs:
A simple 10–20 gallon tank (bare bottom is fine)
A heater and a small sponge filter (pre-seeded in your sump if possible)
A couple of PVC pipes or plastic hides for the fish to feel secure
A lid — stressed fish jump
How long to quarantine: At minimum 4 weeks, ideally 6. During this time you can observe feeding behavior, treat any disease that appears, and ensure the fish is healthy before it ever touches your display tank.
It feels like extra effort — but most hobbyists who skipped QT and lost a tank full of fish wish they hadn't.
