Why Are My Clownfish Fighting?

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Clownfish are among the most popular and beginner-friendly fish for saltwater tanks. These fish are small, non-demanding, and live up to six years!

And besides, who wouldn’t want a sweet Nemo fish to beautify their aquarium display? Clowns are basically the perfect aquarium pet. Or are they?

Well, if you already have some Clownfish, you might have noticed their not-so-perfect behavior. Sometimes, clowns display hostile behaviors towards each other and even other community fish.

It’s not uncommon for Clownfish to chase, bump, and even bite their tankmates. But is this normal, and can you do anything about it? Keep reading to find out!

Are Clownfish Aggressive Fish?

Unfortunately, yes. Despite their innocent appearance, Clownfish are notorious for being aggressive and territorial. This is their natural behavior, whether in the wild or in captivity.

There are two big reasons why Clownfish have such a short fuse:

– They’re native to coral reef habitats

Wild Clownfish live around coral reefs, a hostile environment that houses many opportunistic predators. They’ve had to develop a survival strategy to live in such harsh and competitive conditions.

I guess the best approach is being aggressive when the rule is “hunt or be hunted.”

– They live in hierarchical groups

Clownfish are social animals and prefer living in groups. But unlike other species, Clownfish groups are led by an alpha female.

The dominant female chooses an adult male as a mate, and the fish pair for life. The rest of the group comprises sexually immature male juvenile fish.

The dominant female and male bully the smaller clownfish to establish the social hierarchy. When the dominant female dies, other clownfish will become aggressive and try to take her place.

This in-group aggression keeps the juvenile fish from fully maturing. It’s a way to avoid competition.

These aggressive social and self-preservation behaviors don’t stop once the Clownfish are in captivity. Clownfish still chase away and even fight other fish in the tank to establish their territory. They’re not easily intimidated by tankmates, not even larger fish.

As they mature, Clownfish start bullying each other to establish the social hierarchy. Female Clownfish in particular are relentless and will bully or fight other fish to death.

But the worst violence occurs between members of the same species.

Reasons Clownfish Keep Fighting

Clownfish are naturally aggressive, so fighting is to be expected. Sometimes, certain factors can make their behavior worse.

If the fish are particularly violent and endangering tank members, something more could happen.

Common factors exacerbating Clownfish aggression include:

– Establishing Dominance

If you have two clownfish in the tank, they might not be paired yet. Newly accustomed clownfish take some time to establish dominance in the pair.

This means quite a bit of fighting. Once the dominant female emerges, things should settle down.

The mated pair will bully the submissive fish if you have multiple clownfish together. The in-group fighting never stops, so it’s best to keep only one or two clownfish in a tank.

– Incompatible Tankmates

Clownfish are always on edge, ready to fight. They don’t need much of a reason to act up. If you house the Clownfish with other large or aggressive tankmates, that’s enough to set them off.

Large and boisterous fish will stress out and threaten the Clownfish. This leads to even more aggression, as the Clownfish is trying to stand its ground.

– Exposed Territory

Clownfish are very territorial and like picking their favorite spots in the tank. If you have ornamental caves, live rock, or anemone, chances are your Clownfish hang out around these. They’ll also chase away or fight any fish that approaches.

That’s a problem when the favorite spots of your Clownfish are out in the open.

Placing decorations in the middle of the aquarium means you’ll get a lot of other fish passing by.

Your Clownfish will be on alert to protect their territory at all times, so they will be more aggressive.

– Not Enough Space

Your aquarium could be overstocked. When keeping Clownfish, it’s important to provide enough space to minimize aggression.

A crowded aquarium does the opposite. First, it makes feeding more stressful and competitive.

Secondly, there’s not a lot of swimming room in crowded aquariums. This gives your Clownfish more opportunities to run into other fish in the tank, not necessarily something you want.

You may also have too few hiding spots for all your fish. All of this increases stress, which makes Clownfish more prone to aggression.

– Poor Water Parameters

All fish species have ideal environmental conditions where they thrive. This includes water temperature, pH, salinity, current, and more.

When these parameters are out of range, your clownfish won’t be feeling their best.

Unsuitable nitrates, temperature, and pH, in particular, can devastate your fish. First, improper values stress your fish and encourage aggression.

But even worse, prolonged exposure to such conditions can cause life-threatening health problems.

– Improper Feeding

Ever seen those Snickers commercials? The ones that go: “You’re not you when you’re hungry.” Well, these also apply to grumpy Clownfish.

Feeding your fish too little or choosing the wrong foods can make their mood sour.

“Hangry” Clownfish will cope by becoming aggressive, especially during feeding time.

If your Clownfish start chasing, biting, or fighting their tankmates whenever there’s food around, perhaps it’s time to dial up the portion sizes.

How to Stop Clownfish from Fighting?

Seeing your Clownfish fight all the time is distressing. Constant aggression doesn’t benefit the fish and only increases the risk of physical injury, infections, and premature death.

Luckily, you can do a few things to calm down your feisty Clownfish. Here are some easy ways to stop the fighting:

– Only Keep Two Clownfish at Most

This is the most common advice you’ll hear when stocking a saltwater tank— do NOT keep more than two Clownfish together!

Some aquarists can successfully keep multiple Clownfish. But to ensure minimal aggression, you should stick to only two clownfish.

Once these two form a breeding pair, all other clownfish would be open targets for bullying.

Alternatively, you can always just keep one Clownfish in a community tank. A lone Clownfish won’t cause much trouble if the tankmates are peaceful.

– Provide Enough Space

Your Clownfish need enough room to feel safe and comfortable. For one single clownfish, the minimum tank size is 20 gallons. If you plan to keep a pair, you’ll need 30 gallons total.

Note that these are numbers for the Clownfish only. If you’re adding Clownfish to a community tank, you’ll need enough room to house all the other fish, plus an additional 30 gallons for a clown pair.

– Choose Compatible Tankmates

Clownfish don’t get along with all fish species. You should avoid large and aggressive fish, as these are most likely to pick up a fight with your clowns.

Instead, opt for similar-sized fish with a mild temper. Some good options include Chromis, Royal Grammas, Dartfish, Gobys, and Cardinalfish.

Live anemones are also excellent tankmates for Clownfish. Some of the best anemone species are the Bubble Tip Anemone, the Leathery Sea Anemone, and the Magnificent Anemone.

Bottom-dwelling pets like Hermit crabs, Harlequin shrimps, Peppermint shrimps, and Blood Red shrimps will also get along with clowns. 

– Maintain Good Water Parameters

Water quality is paramount to keeping healthy and happy fish. You want to ensure everything is within the ideal range so your Clownfish feel comfortable in the tank. The cozier the aquarium, the calmer your fish!

The ideal water values for clowns are 74-79°F, 7.8-8.4 pH, 8-12 dGH, and 1.021-1.026 SG.

The ammonia and nitrate levels should be down to 0 ppm. As for water current, Clownfish prefer moderate movement.

– Feed Them Properly

By proper feeding, I mean choosing the right foods and the right portions. Clownfish are omnivorous, so they need a bit of everything. Their wild diet consists of zooplankton, worms, small crustaceans, small fish, and algae.

Emulating their natural diet keeps them satiated and helps them get all the necessary nutrients.

Feed them a variety of protein-rich pellets and wafers. These commercial foods contain a combination of fish, crustaceans, and algae, natural foods that clowns enjoy.

Fresh Mysis and brine shrimp make great protein-rich snacks and are fun for your clowns to eat. You can also supplement your diet with blanched veggies for some extra fiber and vitamins.

Clownfish should eat twice a day. The ideal portion is one your fish can finish in 3 minutes or less.

Remember to disperse the food evenly throughout the tank when feeding your fish. You don’t want all the fish gathering in one spot and fighting for food!

– Add Anemones / Switch Anemone Location

Clownfish and anemones are like a match made in heaven. Whether live or artificial, an anemone makes the perfect spot where clowns can hang out in the tank.

Adding one of these will draw the clowns’ attention from other hiding spots like caves and rocks. This leaves more open territory for other fish, minimizing aggression.

Anemone placement is also important. Since Clownfish will hang out around these decorations, you don’t want to leave them out in the open.

Granted, moving an anemone is easier if you’re using artificial ones. If possible, place these in the back or closer to the sides of the aquarium.

Live anemones are hard to control as they move around the tank alone.

– Buy Captive-Bred Clownfish

Most of the Clownfish sold in the aquarium trade are captive-bred. Why choose captive-bred Clownfish?

Well, these fish grow in safer environments and are less prone to aggression. However, it’s worth double-checking when buying new fish for your community tank.

Besides, captive-bred fish don’t threaten the wild population. Even though Clownfish are currently classified as a species of Least Concern, it’s still a good idea not to harvest wild species for the aquarium trade.

Can Clownfish Kill Each Other?

Yes, Clownfish can kill each other, but this rarely happens. There are only two instances where Clownfish will fight to the death.

This commonly occurs when you have two females in the same tank. Clownfish females cannot live together and will always fight until the dominant female wins.

Clownfish groups can only have one alpha female. All the other fish in the group will be male. The problem is that once a dominant male fish turns into a female, it can’t change its sex back.

So, if you get two female Clownfish, prepare for mayhem. It’s uncommon for two females to emerge in the same tank, though.

You’ll only have to worry about this if you add more adult clowns later.

Clownfish can also fight to the death when two adult males emerge at the same time. Normally, social pressures only allow one male fish to reach sexual maturity.

The other members of the group stay small. But if you have two large male fish, they will fight to establish dominance and mate with the alpha female.

Eventually, the stronger fish wins.

Do Clownfish Fight With Other Fish?

It depends on how compatible the clowns are with their tank mates. Clownfish tend to ignore others. Most of their aggression is directed at other Clownfish.

However, clowns can become aggressive when threatened or provoked. Expect your Clownfish to start a fight if you have other large, territorial, or feisty fish in the tank.

Clownfish are peaceful around other mild-tempered fish, especially if there aren’t other clowns in the tank. If you keep clowns with peaceful community fish, they’re unlikely to cause problems.

If you’re still worried about aggression, choose bottom-dwelling fish. These won’t interact much with your clowns.


Let’s just say that Clownfish are a volatile species. They can get aggressive with each other and even fight other aggressive fish in the tank.

This is normal, as clowns are naturally feisty and trigger-happy. Luckily, you have a few options to correct this behavior.

Lone Clownfish get along well with other peaceful fish like Chromis, Gobies, Cardinalfish, and Dartfish. The best thing you can do is to separate your Clownfish. This will greatly reduce their violent outbursts.

You don’t want to keep more than two clowns together. You can even keep only one clown in the community tank.

Also, you must ensure that your Clownfish are comfortable in the aquarium. Clownfish are less likely to act aggressively if they have enough room.

Remember to maintain stable, species-appropriate water parameters. Also, provide at least 20 gallons of aquarium space for one clown or 30 gallons for a pair.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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