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Are Clownfish Aggressive with Other Fish? 5 Reasons & FAQs

Lindsey Stanton Profile Picture

By Lindsey Stanton


If you are looking to build a saltwater coral reef tank, one type of fish which you are probably tempted to add to the mix is the clownfish. Yes, these are very nice-looking fish. And yes, it’s the same fish as Nemo from the popular kid’s movies. That said, do they get along with others?

So, are clownfish aggressive with other fish? Yes, despite the friendly image they have been given from the Finding Nemo movies, clownfish are actually aggressive towards other fish. Keep reading as we explain further.

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Are Clownfish Actually Aggressive Fish?

Yes, unfortunately, clownfish are usually quite aggressive fish. These fish grow up in coral reefs in the wild, and the coral reef is no place for the faint of heart.

The coral reef is a highly competitive place for any fish to live, with predators always being around the next bend. It’s a relentless fight for survival, and it’s why these fish are so aggressive and territorial. Let’s explain in more detail why clownfish can be so aggressive.

The 5 Reasons Why Your Clownfish is Being Aggressive

There are a variety of reasons why your clownfish may be very aggressive, particularly towards the other fish in the tank. Let’s take a look at all of the different reasons as to why these fish can be so aggressive and territorial.

1. Wild vs Aquarium Raised

One of the main reasons why your clownfish may be very aggressive is because it was caught in the wild as opposed to being born and raised in captivity.

In the wild, the life of a clownfish is one of constant threats. A clownfish has to spend every waking moment ensuring that it stays alive, because everything bigger than it will eat it, at least in the wild on the coral reef. For this reason, wild caught clownfish have to be very aggressive and territorial. If they don’t defend themselves and their homes, they are likely to be eaten or usurped from their homes. It’s nothing personal. It’s all about survival.

clown fish with tropical fish
Image Credit: Anastasia Bulanova, Shutterstock

2. Those Anemones

To dive deeper into the coral reef issue here, the anemones have a big role to play in clownfish aggression. Anemones are those sea creatures you see on coral reefs, with all of those long tubules coming out of them. Each of these offshoots contain poisonous stingers that pack a heck of a punch.

Clownfish have a very interesting relationship with these creatures, as clownfish are immune to the stings of these anemones. These two animals have a symbiotic relationship. Clownfish make their homes and hangout around anemones because other fish don’t dare getting stung, and the anemones feed off of the waste and uneaten food from the clownfish.

Therefore, in the wild, clownfish rely heavily on anemones for survival, and they will defend them with their lives if need be. If you have a wild caught clownfish, the aggression is in part due to this symbiotic relationship. If you have anemones in your aquarium, chances are that the clownfish is being aggressive because it is defending its home and its protector.

3. The Wrong Tank Mates

Clownfish may also become aggressive due to being housed with the wrong tank mates. If clownfish are kept with fish that are also aggressive or territorial, they will get into fights with each other.

Moreover, fish that will harass clownfish or just generally infringe on their space are not good fits and may very well result in aggression.

Small fish tank aquarium with colourful snails and fish at home on wooden table. Fishbowl with freshwater animals in the room
Image Credit: Ja Crispy, Shutterstock

4. A Bad Tank Setup

Clownfish also need the proper tank setup to be happy. Remember that if they don’t have enough coral, the right light, and the right water conditions, they can become stressed out and aggressive.

If you don’t house a clownfish in the environment it feels comfortable in, as well as an environment that is healthy for it, chances are pretty big that the stress this causes them will result in aggression.

5. A Lack of Proper Food

The other reason why clownfish may become aggressive towards other fish is due to a lack of proper food. The fact of the matter is that coral reefs are very competitive places to live, and clownfish have to compete heavily to get enough food to survive.

Therefore, if your clownfish does not have enough food, or if it perceives that it does not have enough food, it will become increasingly aggressive, territorial, and competitive in order to ensure its own survival. Maybe your clownfish is fighting for food.

coral reef colony
Image Credit: videotrinkets, Shutterstock

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How to Reduce Clownfish Aggression

clown fish
Image Credit: Alex Stemmer, Shutterstock

Even though clownfish can be very aggressive and territorial, there are some good ways to ensure that they are less aggressive.

Here are the best things that you as a clownfish owner can do to reduce their aggression:

1. Give Them Lots of Space

Because clownfish are so territorial, particularly with the anemones which they call home, you do want to give these fish lots of space. The more space they have, the less likely they are to come into contact with other fish, and the less likely they are to perceive other fish as threats to their home.

The recommendation is that each clownfish should have 10 gallons of tank space, but if you really want to ensure minimal aggression, go for about 15 gallons of tank space per fish.

2. Feed Them Right

Yes, feeding fish too much can be an issue, as overfeeding can cause health concerns as well as water quality issues. However, if you want to ensure that your clownfish are minimally aggressive, you need to feed them enough.

Feed them more than enough to survive, and then be sure to clean the tank of uneaten food. If the clownfish has no reason to compete for food, it will be much less aggressive.

fish food flakes for tropical fish
Image Credit: Roger Utting, Shutterstock

3. The Right Tank Mates

This is something we will discuss in more detail in the next section below, but the fact remains the same: housing your clownfish with the right tank mates will make a world of difference when it comes to aggressive behavior.

4. Good Water Conditions & Quality

The less stressed out a clownfish is, the less likely it is to be aggressive. So, provide them with plenty of coral and hiding spots, be sure to provide them with lots of good light, keep the water salty, warm, and at the right parameters, and make sure that there is a decent amount of current, not to mention that the water should be kept immaculately clean too.

man conducting ammonia test in front of freshwater aquarium
Image Credit: Ladanifer, Shutterstock

5. Buy Captive Raised Clownfish

As discussed above, clownfish born and raised in captivity are usually much less aggressive than their wild caught counterparts. Therefore, if you want to cut the aggression out right from the get go, buy ones that were bred in captivity.

6. Keep Them in Pairs

A good way to reduce clownfish aggression is to keep them in pairs, with one male and one female.

Clownfish mate for life, so a male and female kept together should get along just fine. However, multiple pairs can be a risky bet, especially if they don’t have enough room.

Clownfish swimming in an aquarium
Image Credit: beto_junior, Shutterstock

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What Fish Can You Put with Clownfish?

Any tank mates you put with your clownfish should be relatively small, peaceful, and they should be fish that are not overly interested in socializing with others or trying to invade the space of others.

Here are some good examples of ideal clownfish tank mates:

  • Chromis Damselfish
  • Pygmy Angelfish
  • Basslets
  • Yellow Tangs
  • Madarin Dragonets
  • Dartfish
  • Red Coris Wrasse
  • Sea Anemones
  • Blood Red Fire Shrimp
  • Hermit Crabs

Can Nemo & Dory Live Together?

Yes, Nemo and Dory can live together. Dory is a Pacific Blue Tang, and they get along fine with clownfish.

Do Clownfish Kill Other Fish?

Yes, clownfish can and do kill other fish, more regularly than most would like to admit. However, this is usually always due to a lack of proper tank space, the wrong tank mates, and being forced to compete for food.

If you follow all of the instructions which we have provided here today, you really should not experience the issue of your clownfish killing another fish.

clown fish with other fish
Image By: Pelagija, Shutterstock

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Final Thoughts

The bottom line is that you do need to take great care and precautions when setting up a clownfish tank. They are aggressive and territorial no doubt. That said, if you do it right, you shouldn’t have any issues, and let’s face it, these are some adorable little fish!

Featured Image Credit: Sebastian Pena Lambarri, Unsplash

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