Most diseases enter an aquarium with a new fish, shrimp, coral or plant. A quarantine tank is a small, separate setup where new arrivals are observed and, if needed, treated before they join your main tank. It is the single best way to protect the livestock you already have.
What you need
A quarantine tank doesn’t need to be pretty:
- A 40–80 L tank or large container with a lid; stressed fish jump
- A sponge filter that has been running in your main tank, so it already has bacteria
- A heater and thermometer (and a refractometer for saltwater)
- A hiding place: a piece of PVC pipe or a clay pot
- A bare bottom, which is easy to clean and medicate
- Nets, a hose and a bucket used only for quarantine
How long to quarantine
- Freshwater fish: at least 2–4 weeks
- Saltwater fish: 4–6 weeks; marine parasites have longer life cycles
- Shrimp and snails: about 3 weeks
- Corals: 4 weeks with repeated dips to catch hatching pests
- Plants: 2–3 weeks in a separate container, or buy tissue-culture plants
Step by step for new fish
- Acclimate: float the bag to match temperature, add tank water slowly over 30–45 minutes, then net the fish across. Don’t pour shop water into your tank.
- Don’t feed on day one. Start with small amounts the next day.
- Test ammonia and nitrite daily in the first week; a quarantine tank has a small bacteria colony.
- Change 25% of the water every 3–4 days and siphon the bottom.
- Observe every day: appetite, breathing, fins, skin, color and behavior.
- If symptoms appear, switch to a treatment plan right away. For example, see white spot.
- If no symptoms appear for the full period, move the fish to the main tank.
Using it as a hospital tank
The same setup works when a fish in your main tank gets sick. Treating in a separate tank means lower medication doses, no harm to plants and invertebrates, and no damage to your main tank’s filter bacteria.
Remove activated carbon when medicating, keep aeration strong and don’t put live rock or sand in a saltwater quarantine tank, because they absorb copper.
Fishtify has a dedicated quarantine mode: create a quarantine tank, choose the livestock, and it builds a day-by-day checklist with the right observation period, water changes and treatment steps.