Can Bleached Acropora Recover?

Looking into your aquarium and noticing your Acropora losing its striking colors, is every coral lover’s nightmare! 

We hear horror stories of coral colonies being wiped out in the wild from coral bleaching, and we pray that it never happens inside our mini-ocean reef aquarium, but it can. 

If coral bleaching does happen inside your aquarium it may feel like all hope is lost, but don’t worry, many experienced hobbyists have also been there. However, pause for a moment and take a deep breath, there are some ways you can help your Acropora coral to recover from bleaching, and we are going to tell you exactly how!

Acropora (Acro) Corals, also known as Staghorn Corals, are the “crown jewels” of the SPS (small polyp tony) world. They are fast growers, making them popular corals for reef tanks, however, they are one of the most challenging SPS corals to keep because of their sensitivity to water chemistry and demanding light and flow requirements. 

Will Bleached Acropora Corals Recover?

Yes, if there are still zooxanthellae left inside your Acro’s tissues, bleached acropora can recover so don’t throw out your Acropora quite yet!

The secret to recovery is tank stability. Creating stable water chemistry, lighting conditions, water flow, and providing nutritional feeding, your Acropora should bounce back in no time.

Recovery of your bleached Acro will depend on the water conditions following the bleaching process, and how severely affected your coral is. As long as you can create a stable environment again, your Acropora should fully recover, however, this will take some time – time is usually the only indication and “cure” to bleached coral recovery. 

Recovery also depends on if “bleaching” is the issue… If your Acropora has turned white overnight, then bleaching may not be the issue. When corals turn ghostly white overnight, it is often rapid tissue necrosis, known as RTN. Bleached Acros can come back. RTN Acros typically won’t. If your Acro is suffering from RTN (or STN – slow tissue necrosis), it will have no more polyps left on its body, therefore it has become just a skeleton, whereas a bleached Acro will still have some tissue left on its skeleton. 

Before we reveal how to recover your sad-looking Acropora, it is important to understand why Corals become bleached. 

Why Do Corals Become Bleached?

Corals contain symbiotic algae in their tissues called zooxanthellae. When corals become stressed, they expel these algae, which causes them to turn white. 

In the wild, Acropora’s limestone skeletons are essential to build reefs around the world, therefore the loss of such fundamental corals like Acropora would have dramatic consequences on marine life and people who rely on fish as a source of protein and income.

Unfortunately, Acros are very prone to coral bleaching because they are heat stress sensitive. When they are faced with bleaching, many colonies become completely bleached and only a handful survive. 

If your Acropora becomes bleached, do not give up yet. Bleached corals are not dead. Many corals can survive bleaching events, however, they do need some extra TLC, as they are under more stress than ever!

We know that keeping corals is no walk in the park. Sometimes we experience swings in water parameters which can affect corals inside our aquariums. Now, we could blame the delivery man for late delivery and/or poor handling, but it is usually the conditions your Acropora is entering (AKA your aquarium) that are most likely the cause of bleaching. 

Not Enough Acro Waste

If your Acro does not produce enough waste, the zooxanthellae inside its tissues will not be happy, and as a result, your poor Acro will not be supported by their symbiotic friends. If your Acro continues to not produce enough waste, three outcomes result in Acropora bleaching:

  • Some zooxanthellae will be released.
  • All the zooxanthellae will be expelled.
  • Your Acro will eat the zooxanthellae as a source of energy.

High Nutrients

Your Acropora requires nutrients to survive, but throw too many at them, you could be waking up to a bleached coral! The more nutrients, the more the zooxanthellae can grow and reproduce, particularly nitrogen. By allowing your nitrogen levels to go off the scale, you are simply adding fuel to a fire. 

When the zooxanthellae receive additional dissolved nitrogen, their growth becomes unbalanced and unchecked, when this happens bleaching is often the only option to stabilize zooxanthellae densities within your coral’s tissues. If you lost me at the chemistry part, all you need to know is that high nitrogen levels are not good and contribute to bleached Acropora Corals. 

Fluctuations In Water Parameters

Acroporas are demanding corals, especially when it comes to temperature, pH, salinity, and alkalinity. Swings in temperatures can easily cause bleaching, particularly when temperatures increase, as increased ocean temperatures from global warming are linked to coral bleaching events

Water parameters such as nitrates and phosphates in the water are also linked to bleaching corals

Excessive Lighting

Too much lighting can be problematic for your Acropora. Elevated lighting causes the zooxanthellae to produce excess oxygen from increased photosynthesis. That may sound like a good thing, but it is not, and to understand why we need to dip our toes into some chemistry – don’t worry I’m no chemistry professor myself, so let’s take a more “simpler” look!

Increased lighting = more photosynthesis (from the zooxanthellae) = more oxygen in the water. Aquarium water (H2O) + oxygen (O2) = hydrogen peroxide (H2O2). Your Acro cannot remove hydrogen peroxide because it does not have little helpers (enzymes) to break down the extra oxygen in hydrogen peroxide. 

If you have ever tried bleaching your hair, hydrogen peroxide would have been used to bleach the hair follicles on your head. So, when your Acropora Coral is exposed to hydrogen peroxide, it bleaches its tissues, eventually poisoning your coral’s cells. 

All these factors can increase stress levels in your Acropora, causing them to expel the zooxanthellae. Without these microscopic algae, your Acro is more susceptible to diseases and can suffer from reduced growth and reproduction rates, and therefore start bleaching

Top Tips To Recover Bleached Acropora Corals!

  • Ensure water parameters are within range by testing them (API test kits are fantastic), send it off for an ICP (inductively coupled plasma) analysis to a water chemistry testing lab for further testing. 
  • Perform a 30-40% water change and re-test the water parameters. 
  • FOOD, FOOD, FOOD! The longer you leave your coral bleached, the more likely it will die of starvation, however, with a decent food source (something meaty), your Acropora should recover within a few weeks or months.
  • Shade them from full light exposure or turn down the light intensity (if you can without harming other corals). It is recommended to get a PAR meter to measure light intensity inside your aquarium – always check the PAR levels for your particular Acropora species too, as this may be where you went wrong. 

Recovering bleached Acropora is not an overnight process, however, if you follow these guidelines, you should see some recovery within weeks, and hopefully a full recovery within months. Be extremely patient and don’t give up, and while it may feel like a long process to recover your bleached Acro, it will be worth it – seeing your Acropora happy again is what we all want!

Summary

If you have a bleached Acropora, the good news is you can recover it, given it hasn’t bleached to the point it has no tissue left on its skeleton or has been mistaken for STN or RTN. 

The “cure” to Acro bleaching is tank stability and time, so with some TLC and patience, your Acropora will be back to normal and showing off those magnificent colors in no time! Check out our ultimate Acropora coral care guide for more information on how to care for these crown jewels.

    by
  • Roy Lee

    I have an unhealthy obsession with reef keeping and maintaining successful tanks. If you haven't noticed from the website, I love everything related to saltwater tanks like coral, fish, and everything else in between.

Leave a Comment