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Why Is My Toadstool Coral Not Opening?

With more and more saltwater aquarium keepers starting to add different types of coral to their tanks, we have seen a spike in the number of different questions that we have seen people from the community asking recently.

Due to toadstool coral also seeing a dramatic increase in its popularity recently too, we have noticed a huge number of questions being asked about caring for toadstool coral too.

One of the most common questions that we see every single month is about toadstool coral not opening when in a tank.

We often see beginners worry that it is due to a problem with their water parameters and end up wasting a huge amount of time looking for the problem when in actual fact, it is totally normal for toadstool corals to periodically close or refuse to open while they shed.

We have decided to publish this article in the hope of being able to help as many of our readers as possible who do keep toadstool coral in their tanks better understand why their toadstool coral will fail to open.

This can help you look for specific causes while also helping your coral shed and get it to open back up sooner rather than later.

Why Is My Toadstool Coral Not Opening?

The most common reason that a toadstool coral will not open is due to it needing to shed the algae built up on it.

You can usually see the waxy coat on the toadstool coral that indicates that is ready to shed and over the course of one week to one month the waxy coat will be released and the toadstool coral will open.

A less common reason that your toadstool coral may not open is due to it getting too much light. This can often be over looked but even in perfect water conditions, if the toadstool coral is getting too much light then it may refuse to open.

If you are not able to see the waxy coat forming on the coral indicating that it is ready to shed then this would be our next thing to check.

In very rare situations, your toadstool coral may be being picked on by the fish in the tank.

Most fish tend to just ignore toadstool coral but there have been a number of reports of certain fish, not specific to a single species that just take a disliking to a toadstool coral in their tank and will actively pick at it.

This will also prevent the toadstool coral from opening too as its defences stay activated and it keeps its toadstool closed down.

“Toadstool coral (Sarcophyton sp.)” by krokodiver is licensed with CC BY 2.0. To view a copy of this license, visit

How Can I Get My Toadstool Coral To Open?

If your toadstool coral appears shiny then it has developed its wax coat to shed as its natural way to remove the growth of both diatom or dino algae.

You can usually help your toadstool coral to gently shed this coat by using a turkey baster with this also helping to prevent the shed from causing issues with your water parameters or irritating other corals in the tank too.

Provided your water parameters are within range for your toadstool coral then the second most common but usually the most difficult issue to fix is the light exposure. Unfortunately, there really isn’t a quick and easy way to fix this one and you just have to experiment with different levels of light exposure.

This can take a surprising amount of time to do but you may be able to speed up the process by making sure the lighting you have for your tank is suitable for a toadstool coral.

If you do notice that your toadstool coral is being bullied by other fish in the tank then you will usually have to decide if you want to remove the fish or the coral. The majority of the time, once a fish has started to pick at a coral it will not stop unless you separate the two.

How Long Will A Toadstool Coral Stay Closed For?

If your toadstool coral is closed due to needing to shed its outer coat then it will usually stay closed for around one week.

If there is an excess of diatom or dino algae in your tank then it can often take as long as a month for the toadstool algae to fully shed its coat and to open up again.

As we mentioned above, you are able to use a turkey baster to help remove the outer coat of your toadstool coral after the first few days of the shedding process.

This can help to get your toadstool coral open much quicker than it otherwise would open, especially if there is a large amount of diatom or dino in the tank.

If your toadstool coral is closed due to there being too much light in the tank or due to one of your fish picking at it then it may stay closed indefinitely.

A number of problems with water parameters can also cause your toadstool coral to close too but once the issues with the tanks water are corrected the toadstool coral will usually open up again within a week.


That brings our article going over why your toadstool coral may not be not opening to an end. We hope that we have been able to help you better understand how you should be trying to correct the issues that cause toadstool corals to close as well as how you are able to better identify each problem. Thankfully, other than the excess of light in the tank, the majority of the problems that will cause a toadstool coral to close can usually be identified with ease.