Coral Acclimation

Acclimating corals—whether introducing new specimens to a reef aquarium or rehabilitating wild fragments—requires a precise, multi-step transition to minimize shock and prevent bleaching. It involves temperature balancing, strict water chemistry matching, pest removal, and light adjustment.

1. Temperature Acclimation

Sudden temperature swings can cause severe cellular stress.

Float the sealed shipping bags in your aquarium for 15–20 minutes. This allows the temperature of the water inside the bag to slowly reach equilibrium with the display tank.
Do not leave bags under intense aquarium lighting during this phase, as the plastic can act as a greenhouse and overheat the water.

2. Parameter & Salinity Matching

Corals are highly sensitive to rapid shifts in salinity, alkalinity, and calcium.

Empty the contents of the shipping bag gently into a clean plastic container or bowl.
Measure the salinity of the shipping water; if it varies significantly from your display tank (by more than 0.002 specific gravity), you will need to acclimate slowly.
Use a drip line to slowly introduce tank water into the container over 30 to 45 minutes, or use a specialized suction-cup acclimation box hung in the tank.

3. Pest Management (Dipping)

To prevent the introduction of nuisance algae, flatworms (such as Acropora-eating flatworms), and other parasites, all new corals should be dipped.

Prepare a coral dip (e.g., Brightwell Aquatics Restora, Seachem Reef Dip, or Two Little Fishies Revive) in a separate container, following the manufacturer’s exact concentration instructions.
Submerge the coral for 5 to 10 minutes, gently swirling it to dislodge any hitchhikers.
Crucial Note: Corals are highly stressed by shipping and immediate dipping can sometimes cause irreversible damage. Some reefkeepers advise waiting 10 to 24 hours after the coral has stabilized in the tank before dipping, though a gentle rinse and inspection immediately out of the bag remains the most common industry standard.
Rinse the coral in fresh saltwater before placing it in the display tank.

4. Placement & Lighting Acclimation

Intense light can shock and quickly bleach newly introduced corals.

Low Light Placement: Place the coral on the sandbed or a low-lit, lower-flow area of the rockscape initially.
Shadowing: Many hobbyists use window screen material over the top of the tank to filter light, removing it layer by layer over a week to help the coral photoacclimate.
Observation: Wait at least a week before permanently gluing the coral down with reef-safe epoxy or cyanoacrylate glue. This ensures the coral is happy with its position and extension.