Quarantine Routine for New Fish and Corals

Most reef pests arrive on something you bought. A fish carries parasites. A coral frag hides a flatworm or a pest snail. Once they reach the display, they are hard to remove. A quarantine tank (QT) gives you a small, separate space to watch new animals before they meet your main tank. It costs little and it prevents a lot of grief.

Set up a simple quarantine tank

Keep it plain. A 40 to 80 litre tank is enough for most fish. Corals can share a smaller one. Use a heater, a thermometer, a gentle filter and a lid. Skip sand and rock, because they make parasites harder to see and treat.

• Bare bottom. You see waste and pests at once, and you can siphon it.
• Hiding places. PVC pipe or a plastic plant gives fish a place to feel safe.
• Cycled filter. Keep a sponge or filter media in your display's sump so it carries bacteria. Move it to the QT before you use it.
• Matching water. Fill with water from the display so salinity, temperature and pH start close to the main tank.

A QT that has not cycled can spike ammonia within days. Our guide to ammonia spikes explains what the numbers mean and how to read them.

How long to quarantine

Most keepers run quarantine for four to six weeks. The time matters more than the method. Many parasites have life cycles of two to four weeks. A short stay can miss them.

Common pests and what they look like

You do not need to name every problem. You need to notice that something changed. Here are the usual suspects reef keepers report.

• Marine ich. Small white spots on fins and body, often with scratching and fast breathing.
• Flatworms. Small, flat, often tan or red worms on corals and glass. Some corals look pale or get a slimy film.
• Acropora-eating flatworms (AEFW). Small brown worms on Acropora that leave pale patches and eggs near the base.
• Nudibranchs and pest snails. Look for small slugs and eggs near the coral base.

Look at new fish every day, and at corals under a torch. A coral dip is a common step for corals before they go into the QT or display. Follow the product label and a trusted source for strength and time. This guide does not give medication doses.

Feed, test and observe

A new animal is stressed. Feed small amounts and remove uneaten food. Test ammonia, nitrite and salinity often. Keep temperature steady, because a swing can set off a disease that was already present. Our guide to temperature stability covers heater and controller setup. When the QT water is stable, you can see the animal more clearly.

Common mistakes to avoid

Three errors cause most quarantine failures. The first is ending the period early because the animal looks fine. Parasites often hide for days. The second is sharing nets, buckets or siphons between the QT and the display. Keep tools separate, or rinse and dry them well. The third is moving water from the QT into the display. Move the animal only, and discard the QT water.

A fourth, quieter mistake is skipping the tank when you are busy. A quarantine you only use sometimes protects you only some of the time. Keep the tank set up and ready, so the next purchase has a place to go.

Keep a quarantine log

Memory fails after three weeks. Write down the date each animal arrived, where it came from, what it ate, what you saw, and every water test. If something fails later, you can look back and see when it started. A log also tells you when the period is truly over.

1. Date in and source of each animal.
2. Daily note: eating, breathing, colour, behaviour.
3. Water tests: ammonia, nitrite, nitrate, salinity, temperature.
4. Any treatment you gave, with date and product.
5. Date out, and a note on how it looked.

When the period ends, move the animal with the same care you would use at acclimation. Then keep logging in ReefDeck, so your QT notes and your display tests sit in one history.