Fast Aquatics

Why quarantine

Every new saltwater fish - even captive-bred, even from premium vendors - can carry parasites and pathogens. Marine ich (Cryptocaryon), velvet (Amyloodinium), Brooklynella, flukes, and uronema are all present in commercial fish supply chains. Once introduced to your display, they're nearly impossible to eradicate without tearing down the entire system.

Freshwater quarantine is also worthwhile but with somewhat lower stakes - most FW pathogens are more easily treated in-display. Marine QT is where the real ROI lives.

Math: a $200 QT tank setup pays for itself the first time it catches a velvet outbreak before that fish enters your display. Velvet kills entire reef tank fish populations in 48-72 hours. There is no cure once it spreads to a tank with corals (you can't hyposalinity or copper-treat a reef).

QT tank setup

  • Tank: 20-40 gallon long, bare bottom (no substrate)
  • Filtration: hang-on-back filter with sponge, OR a fully cycled sponge filter from a seeded source. Skip biological media that absorbs medication (chemipure, carbon)
  • Heater: set to 78-80F
  • Lighting: minimal, just enough for observation
  • Hides: PVC pipe sections (cheap, rinseable, no rock for pathogens to hide in)
  • Salinity: 1.024-1.026 SG matched to your display
  • Test kits: ammonia, nitrite, copper if treating

Observation period

Standard QT runs 4 weeks (28-30 days). The reason: most parasite life cycles are 14-21 days at 78F. A 30-day clean observation (no symptoms, eating well, normal behavior) confirms the fish is parasite-free.

Some keepers extend QT to 76 days for the velvet/ich tomont cycle to fully complete. Shorter QT (14 days) is "soft QT" and increases risk.

Prophylactic treatment

Two camps: observe-only versus treat-prophylactically. The aggressive school treats every new arrival with:

  1. Copper (Coppersafe, Cupramine): 14-21 days at therapeutic dose (1.5-2.0 ppm Coppersafe, 0.5 ppm Cupramine). Treats ich and velvet. Test daily with Hanna or API copper kit. Most marine fish tolerate copper; angels and some butterflyfish do not - use tank-transfer for those.
  2. General Cure (praziquantel + metronidazole): 5 days. Treats internal parasites and flukes.
  3. Formalin or freshwater dip: if Brooklynella suspected (clownfish especially)

Each treatment runs sequentially; do not stack. Allow recovery between treatments. Total prophylactic protocol: ~30-40 days.

Tank-transfer method (for copper-sensitive fish)

For angels, butterflyfish, mandarins, and other copper-intolerant species, use tank transfer for ich:

  1. Two QT tanks set up, fully cycled
  2. Day 1: fish in Tank A
  3. Day 4: transfer fish to Tank B (drained Tank A, restart)
  4. Day 7: transfer back to Tank A
  5. Day 10: transfer to Tank B
  6. Day 13: transfer to Tank A
  7. By Day 13, all ich tomonts have hatched in the previous tank without a host - cycle broken

Observation signs

Daily check for:

  • Eating normally and aggressively
  • No flashing, scratching, or rapid breathing
  • No spots, white film, or velvet sheen
  • Clear eyes, no cloudy eye disease
  • No frayed fins or red sores
  • Normal swimming patterns
  • Normal feces (long stringy white feces = internal parasites)

When QT fails

If a fish shows symptoms during QT, escalate treatment immediately. The QT is doing its job - it caught it. Restart the observation clock after symptoms resolve.

What goes through QT

  • Always: any saltwater fish
  • Recommended: any freshwater fish from a new vendor
  • Optional: invertebrates (most don't carry common fish parasites; CUC is generally safe to skip)
  • Don't QT in copper: coral, anemones, snails, shrimp, crabs - copper kills inverts

The bottom line

Set up a QT tank now. Use it for every new fish. The 30 days you wait will save you years of display tank rebuilds.