You are here:

Saltwater Aquarium/Growth and creature


Purple growths
Purple growths  

Sponge looking growth
Sponge looking growth  
I have a couple of weird growths that I thought might be sponges?? I can not find anything on the internet that really looks like them. My tank has been doing so good. I have a bunch of baby snails and little white star fish. I don't want to take any chances and have some weird growth that will kill everything. Thank u

Hi Debbie:

Always a pleasure to meet another enthusiast.

No cause for alarm, from the images you've provided this is a harmless species of sponge from the indo-pacific. It typically never gets more then an inch thick and it never bothers anything. It's a filter feeder and unless it's causing visible harm you shouldn't be concerned. They are a welcomed addition to most reef microcosms. It actually will help keep live rock together really well, as it grows around and on the underside of live rock. It will also help stable wobbly rocks in your aqua-scape over time.

Having these sponges grow on your rocks is a sign that you're taking great care of your aquarium and water parameters.

Happy Thanksgiving!  

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.