Why Every Reef Keeper Needs a Quarantine Tank
A quarantine tank (QT) is one of the best insurance policies you can have in the saltwater aquarium hobby. It protects your display tank from parasites, diseases, and hitchhikers that can arrive on new fish or invertebrates. A simple, inexpensive QT setup can save you money, livestock, and frustration in the long run.
If you’re just starting out, you may also want to read our guides on setting up a saltwater aquarium and properly acclimating new saltwater fish, which pair perfectly with this quarantine tank guide.
Quarantine Tank Setup: Equipment & Basics
A quarantine tank doesn’t need to be fancy. In fact, simpler is better because it’s easier to keep clean and to medicate when necessary.
Recommended Tank Size
- 10–20 gallons for small reef fish (clownfish, gobies, firefish).
- 20–40 gallons for medium fish (wrasses, dwarf angels, tang juveniles).
Choose a bare-bottom glass tank with no sand or live rock. This prevents parasites from hiding and keeps medications from being absorbed by porous rock.
Essential Equipment
- Heater & thermometer – Stable temperature is critical, especially for stressed new arrivals.
- Sponge filter or simple HOB filter – Seed the media in your display tank or sump for at least a week beforehand to establish beneficial bacteria.
- Air pump – Extra aeration is important when using certain medications.
- PVC elbows or plastic caves – Provide hiding spots that are easy to disinfect.
- Basic LED light – Fish don’t need intense lighting in QT; dim, calm lighting helps reduce stress.
Keep a dedicated set of tools (nets, siphon hose, buckets) for your quarantine tank so you don’t accidentally transfer pathogens back to your display system.
How to Use a Quarantine Tank Effectively
The goal of quarantine is to observe, stabilize, and if needed, treat new fish before they reach your main reef. A standard quarantine period is 4–6 weeks.
Step-by-Step Quarantine Process
- Acclimate slowly: Float the bag to match temperature, then drip-acclimate into a bucket before transferring fish to the QT with a soft net.
- Observe first: For the first 24–48 hours, focus on reducing stress: dim lights, minimal disturbance, and frequent but small feedings.
- Monitor behavior & appearance: Watch for rapid breathing, scratching, white spots, cloudy eyes, frayed fins, or flashing.
- Test water daily: Ammonia is the main threat in a new QT. Perform small, frequent water changes and use a seeded sponge filter to control it.
- Medicate only when appropriate: Follow manufacturer directions carefully, and remove carbon or chemical media when dosing medications.
Pro tip: Feed a variety of foods (frozen, pellets, nori) to help new fish regain strength. A well-fed fish handles treatment and stress far better than a weak one.
Once fish have completed quarantine, are eating aggressively, and show no signs of disease, you can safely transfer them to your display tank using a clean net. Avoid adding QT water to your main system.
Conclusion: Make Quarantine Part of Your Routine
A quarantine tank may feel like an extra step, but it quickly becomes a normal and essential part of responsible reef keeping. By isolating new arrivals, observing them closely, and treating issues early, you dramatically reduce the risk of introducing parasites or diseases into your display tank.
Combine a solid QT routine with good saltwater aquarium maintenance habits, and you’ll enjoy a healthier, more stable reef and far fewer surprises. A little prevention up front is worth far more than emergency treatments later.
Sources
- Humane Society of the United States – Fish health and quarantine best practices.
- Fenner, R. – The Conscientious Marine Aquarist (TFH Publications).
- Noga, E. – Fish Disease: Diagnosis and Treatment (Wiley-Blackwell).
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