Quarantine Tanks: Essential Disease Prevention

Ideal: Keep a cycled sponge filter in your main tank's sump or HOB at all times. When you need QT, move that sponge to the QT tank — it's instantly cycled. Alternatively, you can do a fishless cycle of the QT (2-4 weeks) before your first use. For emergency QT (fish already sick), perform daily 50% water changes and add a bacteria booster (Seachem Stability, FritzZyme) — the QT will not be fully cycled, so you're doing a "fish-in cycle" with medication, which requires vigilance.

1. Acclimation: Float bag for 15 minutes to temperature match. Then drip acclimate for 30-60 minutes using airline tubing with a knot. Never add bag water to QT — it contains shipping ammonia and pathogens.
2. Transfer: Net the fish into QT. Discard all bag water.
3. Observation period (minimum 2 weeks): Watch for flashing, rapid breathing, white spots, stringy feces, clamped fins, or lesions. Feed lightly every other day initially.
4. Prophylactic treatments (optional but recommended): Many advanced hobbyists automatically treat for external parasites (praziquantel) and internal worms (levamisole or fenbendazole in food) during quarantine, regardless of visible symptoms. For community fish, a 2-week observation alone is often sufficient if buying from trusted sources.
5. If symptoms appear: Identify disease and treat accordingly (see our Fish Diseases article). Do not move fish to display until treatment is complete and fish has been symptom-free for 7 days.
6. Release to display: Only after full quarantine period, net fish from QT (don't pour water into display), and release.

After moving fish out, drain the QT completely. Disinfect with a 10% bleach solution (1 part bleach, 9 parts water). Rinse thoroughly, air dry (bleach evaporates). Replace sponge filter or sterilize with bleach and re-cycle. Never reuse a QT without sterilization between batches — pathogens can persist in biofilm.

Plants can carry hitchhikers (snails, hydra, algae spores). Dip plants in a 1:20 bleach:water solution for 90 seconds, then rinse thoroughly, or use alum (1 tablespoon per gallon for 2-3 hours). Invertebrates (shrimp, snails) cannot tolerate many medications. Quarantine them separately in a bare tank for 2 weeks, observing for parasites. Do not co-quarantine fish and inverts.

If you're breeding fish for sale or running a fish store, quarantine is non-negotiable. Implement a three-tier system:

• Level 1: Source quarantine (2 weeks) — New arrivals isolated before entering holding system.
• Level 2: Observation/holding — Healthy fish move here for 1 week before sale.
• Level 3: Treatment/hospital — Separate tank for visibly sick fish.

Use dedicated equipment (nets, siphons) for each zone to prevent cross-contamination. Many stores fail because they skip source quarantine — then one infected shipment contaminates the entire store's central system. For home breeders, a single QT tank is sufficient, but always isolate new breeding stock before adding to your breeding colony.