FishTankHow to set up a quarantine tank
A quarantine tank is a small, simple tank where new fish live for a few weeks before they join your main tank. It's the best way to stop one sick fish from the store wiping out the fish you already have.
Why bother?
Fish from stores often carry parasites and infections that don't show for a week or two. Ich (white spots) is the most common. In a quarantine tank, you can spot problems and treat a few fish, instead of treating your whole display tank. The same tank works as a hospital tank any time a fish gets sick.
What you need
- A small tank with a lid. A 10 gallon is ideal for most small fish. Nervous fish jump, so the lid matters.
- A sponge filter and air pump. Gentle, cheap and easy to clean, and the sponge can live in your main tank between uses.
- A heater and a thermometer.
- A hiding spot, like a clay pot, a piece of pipe or a fake plant. Fish that feel safe stay healthier.
- A bare bottom. No gravel makes it easy to see waste and keep clean.
- Its own net and bucket, so you don't carry anything back to your main tank.
The trick: keep a sponge ready
A quarantine tank needs good bacteria too, or ammonia builds up fast. The easy way: keep a spare sponge filter running in your main tank all the time. It fills up with bacteria. When you bring new fish home, move it to the quarantine tank and it works straight away.
No spare sponge? Use bottled bacteria, feed lightly, and test for ammonia every day or two.
How to quarantine new fish
- Set up the tank with dechlorinated water at the same temperature as your main tank, and move the seeded sponge filter in.
- Acclimate the new fish by floating the bag for 15–20 minutes, then net them into the tank. Don't pour in the store water.
- Watch them every day for about 4 weeks, and never less than 2. Look for white spots, torn fins, fast breathing, rubbing on objects, odd swimming and fish that won't eat.
- Treat only if you see a problem. Some experienced keepers treat every new fish just in case. For beginners, watching closely and treating what you see is simpler and safer.
- Keep the water clean. A small tank gets dirty quickly. Change about 25% of the water a couple of times a week, and feed lightly.
- Move the fish to your main tank once they've been healthy and eating well for at least 2 weeks. Net them across, without any quarantine water.
After quarantine
Put the sponge filter back in your main tank so it stays ready. Empty the quarantine tank and let it dry, or keep it running as a spare. If you treated sick fish in it, clean it out before the next use.
Plants and snails count too. New plants can carry snails, snail eggs and pests. Rinse them well, or keep them in a bucket or the quarantine tank for a couple of weeks. See easy live plants for tips.
Quarantine tank gear
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- Tank kitAqueon 10 gallon starter kit with LED lidA 10 gallon tank, LED lid, filter, preset 50 W heater and thermometer in one box. Swap in a sponge filter for quarantine.
- FilterAQUANEAT sponge filter, small (3 pack)Three small sponge filters. Keep one running in your main tank so it's always ready.
- Air pumpTetra Whisper air pump, 10–30 gallonsPowers the sponge filter.
- HeaterEHEIM Jager 50 W heaterAn adjustable heater, if your tank didn't come with one or you want to set the temperature.
Related: White spots on fish (ich) · How to cycle a new fish tank · Best fish for beginners