How to Set Up a Quarantine Tank (And Why You Need One)

A quarantine tank (QT) is a simple, spare tank you use to house new fish before adding them to your main display tank. It's the single best thing you can do to protect your fish collection. Yet most beginners skip it — until one sick fish wipes out an entire tank.

Why quarantine matters

Fish from the store carry diseases that aren't always visible. Ich (white spot), velvet, flukes, and bacterial infections can all be present in a fish that looks healthy. A 2-4 week quarantine period lets you observe the fish and treat any disease before it spreads to your display tank. One sick fish in a community tank can kill everything in 48 hours.

Setting up a QT: what you need

You need almost nothing: a 10-gallon tank ($15-20), a simple sponge filter (run it in your main tank to seed it with bacteria), a heater, a plain hide (PVC pipe or folded plastic container), and a lid. No substrate. No decorations. This keeps it easy to clean and medicate if needed.

The quarantine protocol

Week 1: Observe new fish. Feed well. Check for spots, rapid breathing, clamped fins, unusual behavior. Week 2: If healthy, you can prophylactically treat with a general anti-parasite medication (Seachem ParaGuard is popular). Week 3-4: Continue observation. If still healthy and eating well, the fish is ready for the display tank.