Quarantine protects your display tank from parasites and bacterial outbreaks. It also gives new fish time to eat well and recover from shipping stress. A simple setup and a clear plan make quarantine easy.
Set up a simple, stable quarantine tank
Use a bare-bottom tank for easy cleaning and observation. A 10 to 20 gallon tank works for most small fish. Use 30 to 40 gallons for tangs and angels. Add a heater, a lid, and a small powerhead. Use an air stone if you medicate.
Filtration matters more than gear. A sponge filter is ideal and cheap. Seed it in your sump for at least two weeks. Keep a second sponge ready for emergencies. If you cannot seed, use bottled bacteria and test daily.
Match display parameters to reduce stress. Aim for 1.025 specific gravity, 78°F, and pH 8.1 to 8.3. Keep ammonia at 0 ppm and nitrite at 0 ppm. Keep nitrate under 20 ppm. Use an ammonia alert badge as a backup.
- Provide PVC elbows for hiding and resting.
- Use a dim light for the first 24 hours.
- Label nets and buckets “QT only” to prevent cross contamination.
If you need a walkthrough, review our quarantine tank setup guide. It covers equipment choices and common sizing mistakes.
Run a 30-day quarantine routine that catches problems early
Start with slow acclimation and calm handling. Float the bag for 15 minutes to equalize temperature. Then drip acclimate for 20 to 30 minutes. Net the fish into QT and discard bag water. This limits pathogen transfer.
Observe first, then treat with a plan. Many hobbyists use a 30-day schedule. Days 1 to 3 focus on feeding and stabilization. Days 4 to 30 focus on observation and targeted treatment. Write notes on appetite, breathing, and spots.
Feed small meals two to three times daily. Offer frozen mysis, enriched brine, and a quality pellet. Add nori for herbivores each morning. Remove uneaten food after five minutes. This keeps ammonia down.
- Test ammonia daily for the first week.
- Change 10% water every two to three days at first.
- Use a white flashlight at night to spot flashing and excess mucus.
For disease recognition, learn the difference between ich and velvet. See our marine ich vs velvet reference. Fast breathing and a “dusty” look need urgent action.
Medication and troubleshooting without crashing the biofilter
Medications work best in a controlled QT. Copper targets ich and velvet, but it must be measured. Use a copper test kit that matches your product. Many chelated coppers target 2.0 to 2.5 ppm. Many ionic coppers target 0.35 to 0.50 ppm. Always follow the label and verify with testing.
Raise copper slowly over 48 hours. This reduces shock in sensitive fish. Keep copper at the therapeutic range for 14 days. Restart the clock if it drops below target. Do not run carbon or GFO during copper treatment. They can strip medication.
Praziquantel helps with flukes and some internal worms. It is often dosed in two rounds, spaced five to seven days apart. Increase aeration during treatment. Watch for oily surface film and low oxygen. If appetite drops, reduce stress and offer live foods.
Ammonia spikes are the most common QT failure. If ammonia hits 0.25 ppm, act fast. Do a 25% water change and add a detoxifier. Reduce feeding for 24 hours. Add a seeded sponge if you have one. Keep a spare heater and air pump ready.
- Never use live rock in medicated QT.
- Do not mix medications unless you know compatibility.
- After QT, sanitize equipment with a mild bleach solution, then dechlorinate.
When symptoms resolve, finish the full observation period. Transfer fish with a clean container, not a net. Avoid moving QT water into the display. For safer transfers, see our how to acclimate fish checklist.
Quarantine takes patience, but it prevents bigger losses. A stable QT and a written routine reduce stress for you and the fish. Your display tank stays healthier and more predictable.
Sources: Colorni, A. (1987) “Biology of Cryptocaryon irritans”; Noga, E.J. (2010) Fish Disease: Diagnosis and Treatment; HumbleFish community quarantine protocols (general methodology).
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