How to Acclimate New Corals
Proper coral acclimation is the process of gradually adjusting new corals to your tank's temperature, water chemistry, and lighting. Rushing this process is one of the most common causes of coral loss. A coral that survives shipping can still die from improper acclimation.
Total time: 1-2 hours initial + 1-2 weeks light acclimation
Why Coral Acclimation Matters
Temperature Shock
Corals shipped in insulated boxes can arrive at temperatures significantly different from your tank. Rapid temperature changes stress coral tissue and can trigger bleaching or death within hours.
Water Chemistry Differences
Shipping water often has different salinity, pH, and alkalinity than your tank. Drip acclimation allows the coral to gradually adjust to these differences rather than experiencing sudden osmotic shock.
Light Shock (Photoshock)
Corals are shipped in dark boxes and from different lighting. Placing them directly under intense reef lighting overwhelms their zooxanthellae, causing stress. Light acclimation is critical but often overlooked.
Step-by-Step Coral Acclimation
Follow these steps for every new coral to maximize survival and minimize stress.
Float the Bag (15-20 minutes)
Float the sealed coral bag in your tank or sump to equalize temperature. Keep your tank lights off during this process to reduce stress on the coral. Temperature shock is one of the fastest ways to damage a coral.
Open and Secure the Bag
Open the bag and roll down the edges to create a floating collar. You can clip it to the tank rim or place it in a container. The goal is to prevent the bag from tipping while allowing you to add tank water.
Begin Drip Acclimation (30-60 minutes)
Using airline tubing with a control valve (or tie a loose knot), start a slow drip of your tank water into the bag. Aim for 2-4 drips per second. This gradually adjusts the coral to your water's salinity, pH, and alkalinity.
Double the Water Volume
Continue dripping until the water in the bag has roughly doubled. This typically takes 30-60 minutes depending on your drip rate. For sensitive corals or large parameter differences, you can extend this phase.
Dip the Coral (Recommended)
Remove the coral from the bag and place it in a coral dip solution (CoralRx, Bayer, or iodine-based) for 5-10 minutes following product instructions. This removes hitchhiker pests that can devastate your tank. Gently shake the coral to dislodge pests.
Initial Placement
Place the coral in a low-light, moderate-flow area of your tank—typically the sandbed or lower rocks. Do NOT place it in its final position yet. The coral needs time to recover from shipping before facing your full lighting.
Light Acclimation (1-2 Weeks)
Over the next 1-2 weeks, gradually move the coral to higher positions with more light. Move it a few inches every 3-4 days, watching for signs of stress. This is the most overlooked step and the most common cause of coral loss.
Common Acclimation Mistakes
Avoid these errors that lead to unnecessary coral loss.
Skipping Light Acclimation
The #1 mistake. Placing corals directly in their "final spot" under full lighting causes photoshock and bleaching. Always start low and move up gradually over 1-2 weeks.
Rushing Temperature Matching
Five minutes isn't enough. Float the sealed bag for a full 15-20 minutes. Temperature shock damages coral cells even if you don't see immediate signs.
Dumping Shipping Water in Tank
Shipping water contains ammonia from the coral's stress, plus potential pathogens and pests. Never pour it into your display tank. Remove the coral and discard the water.
Skipping the Dip
Hitchhiker pests like Acropora-eating flatworms, montipora-eating nudibranchs, and red bugs can devastate your tank. A 5-10 minute dip is cheap insurance.
Signs Your Coral Is Stressed
Watch for these warning signs during and after acclimation. Some stress is normal, but persistent symptoms indicate a problem.
Normal (1-7 days)
- • Polyps remain retracted
- • Reduced coloration
- • Excess mucus production
- • Not accepting food
Concerning (Take Action)
- • Tissue recession or peeling
- • Rapid bleaching (turning white)
- • Brown jelly or white stringy material
- • No improvement after 7+ days
Frequently Asked Questions
How long should I acclimate corals?
Temperature acclimation takes 15-20 minutes. Drip acclimation takes 30-60 minutes until water volume doubles. Light acclimation is the longest phase, taking 1-2 weeks as you gradually move the coral to higher light positions.
Do I need to drip acclimate corals?
Drip acclimation helps corals adjust to differences in salinity, pH, and alkalinity between the shipping water and your tank. While hardy corals may survive without it, drip acclimation significantly reduces stress and improves survival rates, especially for sensitive species.
Should I dip new corals?
Dipping new corals is highly recommended. Coral dips remove hitchhiker pests like flatworms, nudibranchs, and red bugs that can devastate your tank. Popular dips include Coral Rx, Bayer insecticide (diluted), and iodine-based solutions. Always follow product instructions.
Why is my new coral not opening?
New corals often remain closed for 1-7 days after introduction due to shipping stress and environmental adjustment. This is normal. Ensure stable water parameters, low-to-moderate flow, and reduced lighting. If the coral hasn't opened after a week or shows tissue recession, investigate water quality or placement.
Can I skip light acclimation?
Skipping light acclimation is a common cause of coral bleaching and death. Corals shipped in dark boxes have adjusted to zero light. Placing them directly under intense reef lighting causes photoshock and bleaching. Always start low and gradually increase light exposure over 1-2 weeks.
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