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Saltwater Aquarium/Clownfish acting strange


I have a Nano tank (5 gallons) which is host to a juvenile clownfish, some blue-legged hermit crabs and a small anemone. Recently the clownfish has been lying at the bottom of the tank almost regularly. This is not behavior which he exhibited when I first got him about a month ago, nor was it behavior that existed over a week ago. I have brought my water to the pet store countless times for testing and they have found nothing really wrong with it. The only thing that they found once was that my Nitrates were at 10, which is barely anything but I still did a 30% water change. I have had some copepods which bloomed recently and I took that as a good sign that my tank is doing well. My worse issue is my temperature given that the heat from outside can sometimes bring the water temperature higher than it should be.  He is a very picky eater and, since I started giving the anemone brine shrimp, that is really all he wants. He does eat the copepods though. He previously had a mouth fungus and we treated that. Are there any diseases which could result in the clownfish lying on the side and breathing somewhat heavily?

Hi Amber:

Thank you for the question.

It is normal for a clownfish to relax on its side, while in a state of rest. I have a clownfish that rests completely on its side and often times almost motionless. This is also a common occurence for most species of Wrasse fish during the twilight phase of their day. They'll lay on their side in a rock crevice and actually form a cocoon around themselves spun from their own body mucus, in an attempt to stay undected from nocturnal predators that roam their reef habits in the search of a meal.

However note: If you see that your clownfish is experiencing a bacterial infection, fungus, or disease then isolate it in a hospice tank, and treat it accordingly.

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


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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 -

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.

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