Guide — Quarantine Basics

Quarantine Basics

A quarantine tank is your “buffer zone” between the shop and your display tank. It lets you observe new fish, treat problems early and keep parasites and disease out of your main system.

Skipping quarantine can work… until the one time it doesn’t. One bad batch can undo years of work. A simple spare tank is cheap insurance that saves money, stress and fish.

TanksConnected · Risk control

What quarantine protects against

External parasites (whitespot/ich, flukes)
Internal parasites and bacterial infections
Injuries and stress from transport
Chemical residues from shop systems

One small tank can protect your entire collection

Linked guides

Quarantine works best when it’s supported by good water quality and a cycled filter. Your quarantine tank still needs to be treated like a “real” aquarium, not a bucket.

Always recommended

New fish from any shop, breeder or online order.
Fish returning from a show or temporary holding.
Fish that have just recovered from a major treatment.

Especially important

When your display tank is heavily stocked or holds sensitive/expensive species.
When bringing fish from multiple shops/sources at once.
When you’ve recently had any disease outbreak.

Quarantine tank equipment

Basic setup

Spare tank or plastic tub (often 40–80 L for most community fish).
Sponge filter or small internal filter (easy to clean, gentle flow).
Heater with guard (for tropical fish).
Lid/cover to prevent jumping.
Simple hiding places (PVC pipes, plastic pots, fake plants).
Air pump if the filter is air-driven.

Helpful extras

Dedicated net, siphon and bucket (used for QT only).
Spare sponge or media kept cycled in the main filter, ready to move to QT.
Liquid test kit (ammonia, nitrite, nitrate, pH).
Basic meds (whitespot/ich, broad-spectrum anti-bacterial, aquarium salt).

Setting up and running quarantine

1. Prepare the tank

Fill with dechlorinated water, matching temperature to your display tank.
Add pre-cycled sponge/media from your main filter if possible.
Keep décor minimal so you can observe fish easily.
Dim lighting or provide cover to reduce stress.

2. Acclimate new fish

Float the bag to match temperature (10–20 minutes).
Gradually add QT water to the bag or transfer fish and drip-acclimate.
Never pour shop water into your tanks if you can avoid it.

3. Daily routine

Observe behaviour and appetite.
Check for spots, frayed or clamped fins, flashing or gasping.
Feed lightly — in a small QT, overfeeding = instant ammonia spikes.
Test water and change 20–50% as needed to keep ammonia & nitrite at 0.

4. How long to quarantine?

Standard: 2–4 weeks with no visible symptoms.
After treatment: continue at least 1–2 weeks symptom-free before moving fish.
Anything suspicious: extend QT and investigate rather than rushing fish into the display.

Treatment and common mistakes

Using medication in quarantine

QT is the safest place to medicate — no plants, inverts or display bacteria at risk.
Always read the instructions and dose for the actual water volume.
Increase aeration during treatment; many meds reduce oxygen levels.
Remove carbon from the filter if the medication requires it.

Common mistakes

Using the same nets/buckets for QT and display without cleaning.
Overcrowding the quarantine tank with too many new fish at once.
Skipping water tests because “it’s only the QT”.
Dumping unquarantined fish straight into a well-established display tank.

Summary

Quarantine is cheap insurance against disease and parasites.
A basic bare-bones setup is enough — it doesn’t need to be pretty.
Treat and observe fish in QT, not in your display tank.
Keep QT water just as clean and stable as your main tank.

Related guides

New Tank Setup

New tank setup guide

Water Change Guide

Water changes & maintenance

Nitrogen Cycle

Biological filtration explained