How to Acclimate New Fish and Corals
🐠 The short version: new arrivals come from water that differs from yours in temperature, salinity and pH — change all three too fast and you shock them. So float to match temperature, drip-acclimate over ~30–60 minutes, then net the animal in and leave the shop water behind. Inverts and corals need extra care. Acclimation reduces shock; it works hand-in-hand with quarantine.
🔧 Acclimation is step one; quarantine is step two — do both when adding livestock.
Why acclimation matters
A fish, coral or invert arrives in bag water that can differ from your tank in temperature, salinity and pH. Dropped straight in, that sudden change stresses — sometimes kills — the animal, on top of whatever stress the journey already caused. Acclimation simply eases the change so the animal adjusts gradually. It’s a small amount of patience that dramatically improves survival.
The drip method, step by step
This is the reliable, gentle approach for fish, corals and inverts:
- Float to match temperature. Float the sealed bag in the tank (or quarantine tank) for about 15 minutes so temperatures equalise.
- Drip-acclimate. Open the bag or empty it into a small container, and slowly add tank water to it over ~30–60 minutes — a length of airline tubing tied in a loose knot makes a simple drip. This shifts salinity and pH gradually. Confirm your tank’s salinity is on target (~35 ppt) with the salinity converter.
- Net the animal in. Lift a fish out with a net and place it in the tank. Never pour the bag/shop water into your tank — it can carry disease, parasites and pests, and dumps a sudden chemistry change on everything.
- Lights low, no food. Keep lighting dim for the first hours and don’t feed until the animal has settled.
Inverts and corals need extra care
- Inverts (shrimp, snails, crabs) are especially sensitive to salinity shifts — drip them slower and longer. And remember: they’re intolerant of copper, so anything with a copper history is off-limits.
- Corals are acclimated the same gentle way, and many keepers add a brief coral dip to remove pests (flatworms, aiptasia, nuisance hitchhikers) before the coral enters a quarantine/observation tank. Once placed, acclimate corals to your lighting slowly too — new corals can bleach under strong light introduced too fast (lighting guide).
Acclimation and quarantine are different jobs
Don’t confuse the two: acclimation eases the physical change of moving tanks; quarantine watches for and treats disease. They work together — you acclimate a new fish into a quarantine tank, not straight into your display. Skipping either is a common, avoidable way to lose fish or introduce disease.
The honest takeaway
Slow down at the finish line. Float, drip, net (not pour), go gentler still for inverts and corals, and acclimate into quarantine rather than the display. A calm, gradual introduction is one of the cheapest, highest-return habits in the hobby.
Sources & further reading
- Coralkin — How to quarantine new saltwater fish — the step acclimation feeds into.
- Coralkin — Your first saltwater fish — choosing and adding livestock.
- Coralkin — Reef lighting, flow & PAR explained — light-acclimating new corals.
- WetWebMedia — marine acclimation references.
Common questions
What is the drip acclimation method?
You slowly drip your tank water into the bag or container holding the new arrival over roughly 30 to 60 minutes, so it adjusts gradually to your salinity and pH instead of being dropped straight in. Float first to match temperature, then drip, then net the animal into the tank - never pour the shop water in with it.
How long should I acclimate a new fish?
Around 30 to 60 minutes of drip acclimation after floating to match temperature is a good general target. Sensitive inverts like shrimp and snails benefit from a slower, longer drip. The goal is a gradual change in salinity and pH, not a fixed clock.
Why should I never pour the shop water into my tank?
Because that water can carry disease, parasites and pests straight into your display, and it dumps a sudden water-chemistry change on the whole tank. Always net the fish out of its bag water and leave that water behind (or discard it).
Do inverts and corals need different acclimation?
Yes. Inverts (shrimp, snails, crabs) are especially sensitive to salinity swings, so drip them slower and longer. Corals are acclimated similarly, and many keepers also give corals a brief coral dip to remove pests before they go into a quarantine or observation tank, then light-acclimate them slowly once placed.
Should I acclimate into my display or a quarantine tank?
Fish should be acclimated into a quarantine tank, not straight into the display - acclimation and quarantine are two different steps that work together. Corals and inverts go through observation or a dip. Acclimation reduces shock; quarantine keeps disease out.