Good acclimation prevents shock, disease, and early losses. It also helps new fish and corals start eating fast. This guide covers a repeatable process for most marine livestock.
Prep before you open the bag
Plan acclimation before you buy livestock. Keep a clean bucket, airline tubing, and a clip ready. Use a small heater if your room is cool. Dim the lights for the first few hours.
Test your tank first. Aim for 1.024–1.026 specific gravity. Keep temperature at 25–26°C or 77–79°F. Hold pH at 8.1–8.4. Keep ammonia and nitrite at 0 ppm.
Set up a quarantine tank when possible. A simple 10–20 gallon tank works. Use a sponge filter and a heater. Match salinity to the store water on day one.
Do not pour bag water into your display. It can carry ammonia and pathogens. Use a net or specimen cup to move animals. For more on isolation, see quarantine tank basics.
- Have mixed saltwater ready for emergencies and drip waste.
- Keep a towel handy and work near a sink.
- Use a refractometer, not a swing arm hydrometer.
Fish acclimation: float, test, then drip
Start with temperature matching. Float the sealed bag for 15 minutes. Keep the bag out of bright light. This reduces stress and oxygen demand.
Open the bag and test salinity and pH. Many shops run 1.018–1.022 for fish systems. A big jump can burn gills. If the bag smells sharp, ammonia is likely high.
Move fish and bag water into a bucket. Add an airstone if the fish is breathing fast. Start a siphon with airline tubing. Tie a loose knot for flow control.
Drip 2–4 drops per second for most fish. Target 30–45 minutes for small differences. Use 60–90 minutes if salinity differs by 0.004 or more. Discard half the bucket water once, then continue.
- Match salinity within 0.001 before transfer when possible.
- Keep total acclimation under 2 hours for shipping bags.
- Net fish quickly and cover the bucket to prevent jumping.
Release fish with lights low. Do not feed for 4–6 hours. Offer a small meal that night. Watch breathing and flashing for 24 hours. Review marine fish stress signs if behavior looks off.
Corals and inverts: salinity matters, plus dipping
Corals and shrimp hate fast salinity changes. Float for 15 minutes first. Then drip acclimate in a clean container. Use slower flow than fish when in doubt.
For most corals, drip 1–2 drops per second for 30–60 minutes. For sensitive inverts, use 60–120 minutes. Examples include starfish, urchins, and ornamental shrimp. Keep temperature stable during the wait.
Dip corals to reduce pests. Use a coral dip product and follow label timing. Typical dips run 5–10 minutes with gentle swishing. Rinse in clean saltwater before placement.
Place corals low at first. Reduce light by 30–50% for two days. Then ramp up over one week. Keep flow moderate and indirect. For placement basics, see reef lighting acclimation.
- Never expose sponges and tunicates to air.
- Keep starfish fully submerged during transfer.
- Use a turkey baster to blow off pests after dipping.
Troubleshooting and common mistakes
Rushing is the top mistake. A 0.006 salinity jump can cause rapid breathing. Another mistake is long bag acclimation. In shipping water, pH rises after opening. That can convert ammonium into toxic ammonia.
If ammonia is suspected, shorten the process. Temperature match for 10 minutes. Then drip for 15–20 minutes only. Move the animal into clean water fast. Use an ammonia binder in quarantine if needed.
Watch for warning signs. Fish may gasp, clamp fins, or roll. Corals may slime heavily or stay closed. Inverts may fall over and stop moving. Check temperature and salinity immediately.
Stability after acclimation matters most. Keep alkalinity 8–9 dKH for mixed reefs. Keep calcium 400–450 ppm and magnesium 1250–1400 ppm. Avoid big water changes in the first 48 hours.
Sources: Humblefish quarantine and acclimation articles; Borneman, Aquarium Corals (2001); Delbeek & Sprung, The Reef Aquarium Vol. 1 (1994).
A calm, measured acclimation saves livestock. Test first, drip with purpose, and avoid adding bag water. Pair this routine with quarantine and steady parameters. Your new arrivals will settle in faster and stay healthier.
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