How to Treat The Brown Spots on The Clownfish[3 Causes]

Clownfishes are no doubt a delight to have in the aquarium. But sometimes if they are left in the wrong kind of tank conditions then they can quickly develop some brown spots on their body. Most of cases these spots are not fatal to the fish. However, these marks can definitely be a clear indicator of some serious undiscovered problems.

The good news is, in this article, I am going to discuss why Clownfishes are having brown spots and how you can get rid of them in the most simple manner.

Before getting into the article, let’s take a look at the problems and the solution on the spot–



The Clownfish get hurt by corals in the tankPlace some anemones in the tank so that Clownfishes will be less attracted to the corals.
Small tank with unclean waterMake sure the tank has a capacity of at least 30 gallons and change 20-30% of the water every couple of weeks.
The presence of parasitic black ich flatwormsTreat the Clownfish in a formalin bath and disinfect the water with anti-worm products

So, now let’s get into the detailed discussion–

Why Do Clown Fishes Have Brown Spots

spots on clown fishes

There are many reasons for Clownfish to have brown markings on their body. The most frequently occurring reasons are –

  1. If you have corals in your tank then this might be the most common issue. The thing is Clownfishes are not used to living with corals. So, when they are in an aquarium together the Clown fishes are hurt by the coral’s structures because they have a habit of rubbing their body against the corals. 
  2. Another reason for the spots is the dirty tank water. You see, Clownfish and all the other kinds of fish need a clean tank environment. Besides, in a confined space like an aquarium, water tends to get impure with fish excreta and other waste chemicals from fish food and fertilizers very quickly. And this causes irritation in the skin of your Clownfish and results in brown spots. 
  3. Again, if your tank somehow contains (Paravortex turbellaria) then it will cause black and brown spots all over the skin of your Clownfish.

How to Get Rid of The Brown Spots on The Clownfish

Clownfish Freshwater Formalin Dip
  • First, you have to make sure to get rid of the black ich flatworms. For this, you have to transfer your Clownfish to a formalin bath solution for 45-60 minutes. 
  • And to prepare the formalin dip you have to use 1ml of lab-grade formaldehyde with every 10 gallons of water.
  • But the thing is, this formalin solution lowers the oxygen levels very fast so during the dipping period you have to keep the airstone or an aquarium bubbler turned on to maintain the normal oxygen flow.
  • Don’t forget to make sure the temperature of the formalin dip is also similar to the aquarium water so that the Clownfishes don’t go through any kind of stress conditions.
  • After the treatment period is over, transfer the fish to a separate quarantine tank. This is mainly done to avoid any re-infection of flatworms as the main tank is not clean yet.
  • Keep the Clownfishes in the quarantine tank until the black spots disappear and they are feeling better.
  • Meanwhile, you have to clean your main tank and that means getting rid of all the water in it. And make sure you clean the glass surfaces and the stones and all the other hardscapes properly.
  • However, you still cannot be sure whether you have eliminated the flatworms entirely from your tank as they are microscopic in size. So this is why you have to treat the tank water with an anti-worm medication like praziquantel after cleaning up.
  • And the best thing about this product is that it will give complete protection and moreover prevent any future attacks of flatworms in your tank.
  • After adding the Clownfish back into the tank you have to treat the tank water by following the package instructions and add 1-2 grams of this product in every 100 gallons of water twice after 4 days intervals.
  • Before giving the 2nd dose, change at least 70% of the water, and meanwhile don’t forget to monitor your fish so that you can observe how fast they are recovering.
  • Sometimes the brown spots can be some kind of pigmentation due to some natural causes and in this case, the spots are more likely to disappear in a few months on their own.
  • However, you have to closely observe and look for any behavioral changes in the Clownfish. If there aren’t any, you can just leave them swimming freely.
  • Another interesting thing is, that brown spots can also occur if you have a very small tank because when the size is smaller than usual, the Clownfishes feel stressed. So make sure you have a tank that at least has 30 gallons of water holding capacity.
  • Since Clown fishes get bruises while rubbing against the corals it will be a wiser decision to distract them from this activity. And you can do this by placing anemone in the tank because the Clownfishes are usually attracted to them. This is why they are sometimes known as the ”anemonefish”.
  • If the tank has anemones then the Clownfishes can hide around them and won’t go near the corals anymore.
  • And the bruises caused by the corals will slowly heal. For this, you have to keep providing them with enough healthy fish food and nutrients and make sure they are not under any stressful conditions.
  • However, sometimes the anemones can burn the skin of Clownfish in some places and later turn brown, and gradually become black. However, this is not a serious issue and it will not kill your Clownfish. Moreover, the marks will heal with time.
  • Since the skin of Clownfish is very sensitive you have to always make sure the tank water is clean and free of harmful chemicals.
  • Last but not least, try to frequently change the water (at least 20-30% of it) every couple of days. This is also a great way to treat and prevent the brown spots on the Clownfish.


When you notice brown spots starting to grow on your Clownfish you have to treat them as soon as possible since these fishes are very sensitive to adverse conditions. This will be possible only when you inspect your fish tank on a regular basis. 

Isolate them at the first sight of brown spots and shift them to a separate container before the marks can spread to other healthy fishes in your tank. After that, treat them in the way that feels most convenient to you with the help of this article. 

I hope you found this piece helpful while removing the brown spots from the Clownfish.

Howard Parker

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