The single best habit in fishkeeping is quarantining new arrivals — because one unquarantined fish can introduce ich, velvet or worse and wipe out an established tank. A quarantine setup is cheap, simple, and the insurance that protects everything else you have built. This UK guide covers the best quarantine kit in 2026.
Here’s what you need.
- Quarantining new fish is the best habit in the hobby — it stops disease reaching your main tank.
- A bare 20–40 litre tank with a sponge filter and heater is all you need.
- Seed the sponge filter in your main tank first for instant beneficial bacteria.
- Keep new fish in quarantine two to four weeks before moving them across.
Why quarantine matters
Shop tanks are often shared water systems where disease spreads easily, and new fish are stressed and prone to outbreaks. Two to four weeks in a separate tank lets problems show and be treated before they ever reach your main aquarium. See our full quarantine tank setup guide.
The kit you need
A simple tank. A bare small tank of 20–40 litres is plenty — no substrate, for easy cleaning.
A sponge filter — a sponge filter run in your main tank beforehand seeds it with beneficial bacteria instantly.
A heater — a small heater to hold a stable, treatment-friendly temperature.
Hiding places and a lid — simple cover reduces stress. Keep basic medications and a test kit on hand.
How to run it
Keep new fish in quarantine for two to four weeks, watching for signs of disease. Feed lightly, test water, and do regular small water changes. Only move fish to the main tank once they have eaten well and shown no symptoms. Keep the seeded sponge filter running in your main tank between uses so the quarantine tank is ready at short notice.
Frequently asked questions
Why do I need a quarantine tank?
Because one unquarantined new fish can introduce ich, velvet or other diseases and wipe out an established tank. Two to four weeks in a separate tank lets problems show and be treated first.
What do I need for a quarantine tank?
A bare small tank of 20–40 litres, a sponge filter (ideally seeded in your main tank beforehand), a heater, simple hiding places, a lid, and basic medications and a test kit on hand.
How long should fish stay in quarantine?
Two to four weeks. Only move fish to your main tank once they have eaten well and shown no signs of disease throughout the quarantine period.
— Jaqline Smalling, FishForever
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