Why Is My Mushroom Coral Shrinking?

Has one or more of your mushroom corals shrunk or shriveled up all of a sudden, and you have no idea why? 

If so, you have come to the right place, as I am here to tell you what may have caused it and what you can do to get your mushroom coral happy and healthy again. 

Why Do Mushroom Corals Shrink?

Often, many hobbyists forget or do not even know that corals are, in fact, animals not plants, therefore they have specific needs just like you and me. 

Common reasons mushroom corals may start shrinking:

  1. Too much light
  2. Not enough water flow 
  3. Poor water conditions
  4. Poor nutrition
  5. Disturbance
  6. Acclimation

1. Too Much Light

Shrinking mushrooms are usually associated with too much light. When corals are happy, they will extend their polyps towards the lighting, not the opposite. So, if your mushroom coral is shrinking, and you have tested the water parameters, lighting is probably the main issue!

As mushroom corals can move, they do tend to move away from intense lighting. However, if your mushroom coral has decided to stay put, move it to a shaded area and turn the lighting down if you can. 

So, how much lighting do mushroom corals need?

Mushrooms thrive with a low PAR level between 50 and 150, but some can tolerate stronger lighting, so always check which type of mushroom coral you have. 

2. Not Enough Water Flow

Your mushroom coral loves a gentle water flow, but this doesn’t mean they should be kept where they are living in stagnant conditions. Not only does the water flow keep debris like fish poop and uneaten food off your mushroom coral’s delicate polyps, but it also keeps nutrients and trace elements cycled around the aquarium. 

If your mushroom is in an area where it is not receiving enough water flow it may move, but if it doesn’t, either move it to an area with more flow (be careful to not move it too close to the lighting fixture) or increase the power of your water pump – just be careful not to also blast your mushroom coral, as this can tear its tissues. 

3. Poor Water Conditions

In addition to correct lighting, your mushroom coral requires certain conditions. Mushroom corals may be able to tolerate small changes in water parameters, but if they fluctuate too much, and you skipped that last water change, test your water conditions as soon as possible. 

Providing a stable environment is key to successfully keeping corals, that also includes more forgiving corals like your mushroom. Maintaining a stable environment is also important for your mushroom coral to grow.

Ideal Water Parameters:

  • Temperature: 76° – 82 °F
  • pH: 8.1 – 8.4
  • Salinity: 1.023 – 1.025
  • Alkalinity: 9 – 11 dKH
  • Nitrates: <10 ppm
  • Phosphates: <10 ppm
  • Calcium: 350 – 450 ppm
  • Magnesium: 1250 – 1350

The common offenders are usually pH, alkalinity, and nitrate.

  • For pH, add a buffer to replenish the carbonate and bicarbonate.
  • If alkalinity drops are an issue, increase the alkalinity by performing water changes and adding chemical buffers. Alkalinity constantly decreases in aquariums as biological processes remove carbonate, and in return, acid is produced, which neutralizes carbonate. 
  • If you have a spike in nitrates, add a nitrate remover like ‘ALGONE’, reduce the amount of fish in your aquarium or get a bigger tank, reduce your feeding, or you can add live plants such as the popular green finger plant or the beautiful mermaid’s fan.

4. Poor Nutrition

Although your mushroom coral gets most of its nutrition (around 80%) from the zooxanthellae that live inside your coral’s tissues, mushroom corals are also able to catch food and eat. 

Mushroom corals can either be target fed or fed via the broadcasting method, however, as they have small mouths, target feeding is recommended. Your mushroom coral can be fed 1-2 times per week with something meaty like phytoplankton, rotifers, or mysis. Foods like Oyster-Feast, TDO Chroma Boost, and Coral Frenzy will cover your mushroom coral’s nutritional needs. 

5. Disturbance

Although mushroom corals are not considered aggressive, their neighbors may be, and if they take a swing at your mushroom coral it may start shriveling up and shrinking. How would you like it if someone hit you with a giant pool noodle… I’m sure you would also shrivel up into a ball to protect yourself. 

If coral compatibility is an issue inside your reef aquarium, consider moving aggressive corals to a different area or remove them completely if they are starting to damage your mushroom coral or other corals. 

Now, if you have fish, you can’t put all the blame on the corals, as some fish will nip at corals the minute you turn your back or go to bed. Always check with your local fish store that the fish you have are compatible with the corals you have in your aquarium. 

6. Acclimation

Ok, so you have checked all the above and everything seems stable, but still, your mushroom coral is shrinking…

If your mushroom coral is not responding after a couple of weeks, it may be that it needs to acclimate a little longer. Some mushroom corals take longer to acclimate to captivity, particularly if they have been caught from the wild instead of aquacultured in captivity. 

When newly added corals are placed in an aquarium, they take a while to get used to their new environment. You should always start off placing your mushroom coral lower down in the aquarium or under low lighting for a few days. This prevents mushroom corals from turning white


Mushroom corals are hardy corals, however, if they feel uncomfortable they can start to shrink. 

This is usually from too much lighting, but poor water quality, skipping/improper acclimation, pesky neighbors, not enough water flow, and poor nutrition are also linked to mushroom corals shrinking. 

Once you have identified the issue and resolved it, your mushroom coral should be back to normal in a few days!

  • 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.

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