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How Long Does It Take for Corals To Open Up?

Every aquarist’s primary goal is to have their aquarium look as good as possible. In addition to adding shiny fish and flashy decorative elements, corals are one of the best ways to spruce up your aquarium. Still you might be wondering if it will take ages to open up once you bring it in? 

Quick Answer

It takes an average of two days for corals to open up. Depending on the type, corals can take anywhere between a few hours and a few weeks to open. Corals kept in an aquarium have such a different opening time due to factors other than their species. The primary ones are water quality and lighting.

In this article, I will explore the elements behind corals’ opening time and, as well as explain what you can do to ensure that the opening occurs. 

Factors That Affect Coral Opening Times

Introducing corals is one of the best things you can do for your aquarium as they help purify the water in the tank and provide fish with a place to hide during their down period. 

Corals can be introduced to any saltwater aquarium, but adding them to a freshwater environment, on the other hand, will almost certainly negatively affect the entire ecosystem. 

The saltwater surroundings will ensure that they open up fairly quickly. Though, as I stated above, the opening time for corals can depend on various elements, including:

  • Their species 
  • The quality of the water they’re growing in 
  • The acclimation process they’ve undergone 
  • The lighting they receive 
  • The water flow they’re exposed to 

If you want to be sure your aquarium is ready for new coral, make sure to read this article on my website.

Based on these factors, corals can open anywhere from an hour or two to over a week before they start opening up. 

Here is a short guide on what the optimal parameters for coral development are, based LiveAquaria data

ParameterAverage Level for Coral Reefs
Water Temperature82°F (28°C)
pH8.0 – 8.5
Alkalinity6 – 8 dKH
Ammonia (NH3)Near Zero
Nitrite (NO2)Near Zero
Nitrate (NO3)0.25 ppm
Phosphate0.13 ppm
Calcium380 – 420 ppm
Magnesium1300 ppm
Iodine0.06 ppm

By ensuring that all of these parameters are met, coral enthusiasts can rest assured that their new pet can thrive and open up as quickly as possible. 

How Long Can a Coral Stay Closed?

In the wild, coral reefs can take anywhere between 100,000 to 30,000,000 years to form. But in a reef aquarium, most owners should see signs of opening after just a few hours. That said, some species can take weeks to finally open.

Suppose you’ve followed all of the suggestions from the previous paragraphs. In that case, you should start looking forward to the corals’ opening up reasonably soon. The lucky few will get to enjoy their corals’ full beauty in a matter of hours. 

On the other hand, some corals can stay closed for multiple weeks. According to some aquarists’ experience, corals such as Hammer Coral (Euphyllia ancora) can take up to three weeks to open fully. 

The important thing is to not give up on proper care after you’ve noticed nothing has happened seven days after the introduction to the tank. Just give them time and the care they need, and everything should work out fine. 

However, what happens when you’ve given them time, and they still aren’t opening? 

Why Aren’t My Corals Opening?

If your corals aren’t opening, try to give them extra time. If they have been properly acclimated, they should open when they’re ready. However, the problem could be more complex, such as receiving a bad batch of livestock or making basic mistakes during the introduction procedure. 

There are plenty of things that can go wrong and prevent your corals from opening up. The most common one is also the simplest – they might need more time. Just be patient and wait them out.

In case you’re suspecting that something might be wrong with your new corals, there might be a few things you could have done differently. So, let’s briefly discuss the proper procedure of coral integration. 

How to Acclimate Corals to Your Tank

Like any other living organism you bring into your aquarium, you need to give corals an acclimation window. Here are a few steps you should be following to ensure your corals open up as soon as possible: 

  1. Introduce the corals into the environment the right way: The first thing to do once the corals have arrived is to allow them around 30 minutes of quiet time in either your display tank or the QT tank without opening the bag they came in. Afterward, you can open the bag and start adding a quarter to a half cup (60 to 118 mL) of water. Experts suggest repeating this procedure up to five times over two hours. 
  1. Start with the lights off: Traveling to you, corals have spent at least a day in a dark environment. Tidal Gardens explains that exposing corals to a beaming aquarium might be causing stress and preventing them from opening up. The light might cause irreversible damage to the livestock in a matter of hours. Instead, bring in the light gradually over the next two to three days. 
  1. Keep the water flow up: Optimal CO2 and O2 levels are two significant factors for coral development. If you’re wondering why the corals aren’t opening, one of the reasons might be that the balance of these gasses in the tank is off due to the insufficient water flow, preventing respiration and photosynthesis. 

As evident from everything written above, corals can get a little fussy. From hitting the sweet spot with the water temperature and pH levels to finding the proper lighting and water pressure, caring for corals is far from easy. 


You don’t need to spend hundreds of dollars on an aquarium to make it pretty. Spending just a fraction of that cost can buy you a ton of corals while making the tank unique and stunning. 

It should be kept in mind that corals, just like fish, require some time and effort. With corals, you’ll be investing most of that time and effort when preparing the aquarium for their arrival.

As long as you follow the tips from this article, your corals will open quickly, and your own coral reef should be in full swing in a matter of days.