Saltwater Aquarium/strange growth


odd growth
odd growth  
Hi,I'm hoping u can identity this strange round purple growth in the centre of my picture seems almost a white fungus growth underneath,yet the top seems almost rubbery and very deep purple.its roughly the size of a little finger nail at the moment,but growing quite quickly.I noticed it about a month ago and to hours of research on internet,I cannot find anything simular.please identify this for me and possibly others..many thanks.

Good morning Craig:

From the image that you've provided I have determined that this is a species of sponge. However they are harmless, and make great additions to most saltwater aquariums because they filter particulates out of the water as their main food source, and they also help to bond live rock together, as they kind of act as a masonry mortar in between rocks.

In nature, they are considered food items for many fish and invertebrate, for example pencil urchins eat sponge, and sponges make up the majority, 70 95%, of the diet of most angelfishes (Family Pomacanthidae).

Some species of sponge are highly prized and sought after in the saltwater aquarium hobby, including species of blue, yellow and pink sponge.

Thanks for the question.

I wish you luck with all your saltwater aquarium endeavors.


All Experts - Editor

Director of Operations - Orange County Reef Aquatics (

Saltwater Aquarium

All Answers

Answers by Expert:

Ask Experts


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 -

Publications,, and many others.

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.

©2017 All rights reserved.