Bringing home a new saltwater fish is exciting. It is also when most losses happen. Use this checklist to reduce stress and prevent disease.

Before you open the bag: prep and planning

Start with a quarantine tank if you can. A 10–20 gallon tank works for most small fish. Use a heater, a lid, and a sponge filter. Seed the sponge in your sump for two weeks.

Match basic parameters before the fish arrives. Aim for 78°F, salinity 1.025, and pH 8.1–8.4. Keep ammonia and nitrite at 0 ppm. Keep nitrate under 20 ppm in quarantine.

Dim the lights in the room and tank. Turn off display lights for the first day. Stress drops fast in low light. Have a clean bucket, airline tubing, and a clip ready.

Plan where the fish will go. Avoid adding it to a crowded tank. Rearrange one rock if you expect aggression. Review your quarantine tank setup ahead of time.

• Mix extra saltwater for emergencies and water changes.
• Prepare an ammonia binder for transport water spikes.
• Keep a small net and a specimen container ready.

Acclimation steps: temperature, salinity, and safe transfer

Float the sealed bag for 15–20 minutes. This stabilizes temperature. Do not float longer than 30 minutes. CO2 drops and pH can rise fast in the bag.

Open the bag and test salinity if possible. Many stores run 1.018–1.022. Your reef may be 1.025. Large jumps can shock gills and kidneys. Drip acclimation helps with salinity differences.

Place the fish and bag water into a clean bucket. Clip airline tubing from the tank to the bucket. Tie a loose knot for a slow drip. Target 2–4 drops per second for 30–45 minutes.

When bucket volume doubles, remove half and continue. Stop when salinity is within 0.001 specific gravity. Then transfer the fish without adding bag water. Use a specimen cup, not a net, for delicate fish.

• If the bag smells sharp, shorten acclimation and prioritize clean water.
• If the fish is gasping, increase surface agitation right away.
• Never pour store water into your display or quarantine.

First 72 hours: observation, feeding, and troubleshooting

Give the fish a calm first day. Keep lights low and flow moderate. Provide a hiding spot like PVC elbows in quarantine. Watch breathing rate and posture. Rapid gill movement can signal ammonia or parasites.

Test ammonia twice daily in quarantine for the first week. Keep it at 0 ppm. If you see 0.25 ppm, do a 25–50% water change. Add bottled bacteria if needed. A seeded sponge filter helps most.

Feed small meals after a few hours. Offer frozen mysis, brine, or pellets. Try two tiny feedings per day. Remove leftovers after five minutes. A new fish often eats better with competition, but quarantine is safer.

Look for early disease signs. White dots can mean ich. Dusty gold can mean velvet. Excess mucus can mean flukes. If symptoms appear, act fast. Review our ich vs velvet guide and keep a plan ready.

• Common mistake: adding the fish during peak lighting hours.
• Common mistake: skipping quarantine for “healthy looking” fish.
• Common mistake: drip acclimating for hours in dirty bag water.

If you must add to the display, reduce aggression. Feed the tank first. Use an acclimation box for 24–72 hours. This helps tangs and wrasses settle. You can read more in our new fish introduction tips.

Track results in a log. Record salinity, temperature, and feeding response. Note any spots, flashing, or clamped fins. Patterns appear quickly with good notes. This makes future additions much easier.

Sources: Humblefish Disease Forum (quarantine methods overview); NOAA Reef Fish Health references (stress and water quality basics); Noga, “Fish Disease: Diagnosis and Treatment” (clinical signs and management).

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