Saltwater Aquarium/Growth in tank


QUESTION: My 55 gallon tank (4years old) has begun producing multiple growths as noted in the picture below. The first one was present in the tank for about a year at the same size. Over the past few months, we have noticed many more popping up. Cream colored and about the size of a dime. Any idea what these are and are they safe for the tank?? Thank you in advance. Nicci

ANSWER: Hi Nicci:

From what you have described it sounds like they are harmless sponges.

I wish you the best of luck with all your saltwater aquarium endeavors.


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Thank you for the response. After I hit the send button yesterday, I realized I had not enclosed pics. Please review and let me know if you still feel they are harmless sponges. There are quite a few in the tank in varying stages of development and some have holes on the sides of them?? Thanks in advance for your time and expertise.

Hi Nicci:

From looking at the images, I can confirm that it's definitely sponges. These are a welcomed addition to a reef aquarium. You have nothing to worry about.

In the reef aquarium hobby, species of blue, yellow, and red sponges are highly sought after.

In nature, in the oceans coral reef's, sponges are a food item for many types of fish, including many species of Angel fish.


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David Ocreef


Technical saltwater coral reef related aquarium questions are welcome. Coral, invertebrate, and peaceful species of saltwater fish questions are welcome. Questions asked on Saturday and Sunday will be answered the following Monday. REMINDER: Please check the answers pool to see if your question has already been asked and answered. Questions typically are answered within a 48 hour period, however sometimes it may take longer.


I possess over twenty-five years of hands-on experience and knowledge in the ecology of aquariums. Beyond the traditional, I have successfully tested and sustained environments that have been uncharted territories for hobbyists, for decades. I am the first to admit I don't know it all because there will always be something new, amazing, and exciting to learn about, as discoveries are made. It's a hobby one can never outgrow, or grow tired of.

MASNA - Marine Aquarium Society of North America. Director of Orange County Reef Aquatics -

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After High School, my experience and love of marine animals influenced me to take up studies in Marine Biology. Throughout college, I studied Microbiology with an emphasis on Marine Life, as well as numerous other sciences. I continued to advance in this hobby, by building a dozen or more saltwater ecosystems all utilizing Microbes as the major source of my filtration method.

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