Plan ahead

Quarantine for marine fish and corals: a realistic guide

Quarantine means keeping new animals apart until disease and pests show themselves. It is the step keepers skip most and regret most. This page sets out the options, from buying fish a shop has already quarantined to a full copper treatment, so you can pick one you will actually do. Setting up a new tank? Start with stage 8 of the setup path, which builds the quarantine tank before your first fish.

Last checked 21 October 2026. How we check

Why quarantine at all?

Reef Builders lists skipping dips and quarantine among the top beginner mistakes. Once marine whitespot or velvet is in a display, every fish has to come out and the tank has to run without fish for weeks. Pests on corals are similar: once Acropora-eating flatworms or Montipora nudibranchs breed in the display, they are very hard to remove.

What are the quarantine options for fish?

BRS’s fish addition guide suggests about 15 days of quarantine but also observing for at least 30, without reconciling the two. When the fish leaves quarantine, BRS suggests a 30 to 60 second rinse in clean salt water and, in an established tank, an acclimation box so residents do not bully it.

What does a quarantine tank need?

Which fish need extra care in quarantine?

• Copper-sensitive fish: dwarf angels such as the flame angel, coral beauty and cherub angel; anthias such as the lyretail anthias; fairy wrasses such as the red head solon fairy wrasse; and mandarins. LiveAquaria advises keeping copper under 0.15 ppm for flame angels.
• Tangs: the classic ich carriers (LiveAquaria). The regal blue tang and yellow tang are worth the full routine.
• Clownfish: wild-caught clownfish are often reported with Brooklynella (keeper reports, typical, check), a reason to buy captive-bred such as the ocellaris clownfish.
• Specialist feeders: mandarins do badly in a bare tank unless they already eat frozen food (our reading).
• Sand sleepers and burrowers: wrasses and the yellowhead jawfish need a dish of sand.

How do I quarantine corals?

1. Dip on arrival, following the dip’s label. See what each dip does.
2. Remove the frag from its plug where you can, and look at the underside, the plug and the glue line (BRS).
3. Inspect each frag in the morning and again after lights out with a torch (BRS).
4. Re-dip whenever you see pests, and add four weeks after each new round (BRS).
5. Hold for 4 to 8 weeks or longer (BRS). For Acropora, time the second treatment around the flatworm egg cycle (see below).

A 2019 study of Acropora-eating flatworms found eggs took about 26 days to hatch at 21 C, 15 at 24 C, 11 at 27 C and 9 at 30 C. The authors advise re-treating after the eggs hatch and before the new worms mature, about 13 to 31 days after the first treatment at 28 C, and keeping corals out of the display between treatments.

No quarantine is perfect: dips do not kill eggs, and tiny larvae can get through. It lowers the risk; it does not remove it.

What about snails, crabs and shrimp?

Copper and most fish medicines kill invertebrates, so they can never share a treated quarantine tank. They also cannot be dipped like corals. Our reading: acclimate them slowly, look them over for hitchhikers, and keep them apart for a couple of weeks if you can. Some keepers hold corals and invertebrates for about 72 to 76 days so that any fish parasites in the water die out (typical, check).

Where do sources disagree?