Aggressive Freshwater Fish

Do you know that if your water is not in the desired PH range as per your fish, it can cause some problems like Algae Growth, Coral Growth, damage to the health of your fish, etc. We would highly recommend getting this API Water Testing Kit on Amazon.com, so you’re always aware of the pH level of your aquarium.

Fish are animals and aggression is a part of the life of any animal. Some animals are more aggressive than others, including fish.

Check out 16 of the Most Aggressive Animals.

It is very important to know which fish species are aggressive and how to avoid disastrous combinations of keeping fish in the same tank resulting in the death of multiple fish.

Aggressive freshwater fish may receive a poor reputation by some people due to a bad experience, prejudice, or not enough knowledge about fish behavior, requirements, and suitable tank mates.

That’s why it is important for you to know the different types of aggressive freshwater fish.

Aggressive Freshwater Fish - Blue Peacock Cichlid

Why are some fish aggressive or semi-aggressive?

Animals live on instinct and the law of survival of the fittest still applies in the animal kingdom.

Aggression is a behavior that is developed throughout the evolution of the fish species and can develop even in the most peaceful species of fish; the conditions fish live in may dictate whether the fish will become aggressive to survive.

Harsh environments and lack of food can lead to developing aggression needed for survival.

Aggression occurs when fish are feeding, mating, or simply defending their territory.

Aggressive fish are kept in fish tanks all over the world

Just because a fish is aggressive, fish enthusiasts may still keep them.

Even the most aggressive freshwater fish are beautifully rich in color and when kept with suitable tank mates can be part of a great aquarium.

Some people like aggressive fish and predator fish in their tanks.

Aggressive fish tend to be territorial, fight over food, fight when mating, and attack other fish.

Predator fish feed on live fish, but aggressive behavior is not equal to predatory behavior.

For example, you may keep predators who seem to get along just fine and when they eat live fish they behave like predators, but aggression is when they attack other fish over food.

Some fish can be extremely aggressive but aren’t predators. Types of aggressive freshwater fish are:

Aggressive Freshwater Fish - Vampire Tetra

Types of aggressive freshwater fish

Predators

Goliath tigerfish, vampire tetra, snakehead fish, peacock bass, giant wolf fish, alligator gar, Arowana, and Piranhas, especially the red belly and black piranha. These are voracious carnivores favoring a meat-based diet.

Cichlids

Most cichlids are aggressive, territorial, bite, kill, and eat or fight other cichlids and fish.  Yet, some types of peaceful cichlids are considered good parents and they aggressively defend their offspring.

Species of aggressive cichlids

American Species Dovii (Parachromis dovii), Jaguar cichlid (Parachromis managuensis), Midas cichlid (Cichlasoma citrinellum), Salvin’s cichlid (Cichlasoma salvini), Blackbelt cichlid (Cichlasoma maculicauda), Red devil (Cichlasoma labiatum), Oscar (Astronotus ocellatus), Green terror cichlid (Andinoacara rivulatus), Jack Dempsey cichlid (Cichlasoma octofasciatum), Texas cichlid (Cichlasoma cyanoguttatum), Firemouth cichlid (Thorichthys meeki), and Convict cichlid (Cichlasoma nigrofasciatum)
African Species Jewel cichlid (Hemichromis), Frontosa (Cyphotilapia frontosa), Tetracanthus (Neolamprologus tetracanthus), Lemon cichlid (Neolamprologus leleupi), Five-barred cichlid (Neolamprologus tretocephalus), Nyassa peacock (Aulonocara nyassae), Malawian eye-biter (Dimidiochromis compressiceps), Malawi golden cichlid (Melanochromis auratus), Melanochromis johannii, Cobalt blue cichlid (Pseudotropheus socolofi), and most Mbunas cichlids are considered semi-aggressive, but there are also aggressive ones.
Others Parrot cichlid (a hybrid of midas and redhead cichlid)

Species of fairly calm temperament cichlids

German ram (Mikrogeophagus ramirezi), Angel fish (Pterophyllum scalare) are considered peaceful except during spawning, the beautiful Discus fish, Agassiz’s dwarf cichlid (Apistogramma agassizii), Dwarf shell-dweller (Neolamprologus brevis), Two-spot cichlid (Cichlasoma bimaculatum), Severum cichlid (Heros severum) are relatively calm, except during spawning, Redheaded cichlid (Cichlasoma synspilum) is fairly well behaved with other species despite its large size (11 inches) provided it respects its territory.

Tiger Barbs

These small schooling fish that nip the fins of long-finned fish and males are aggressive towards females when mating.

Aggressive Freshwater Fish - Tiger Barb

Betta Fish/Siamese Fighting Fish

Male Betta fish are very common small fish that behave quite aggressively towards each other and will fight one another to death.

Also, a male will fight with a female to death unless the two are mating; however, when mating is finished, they should be separated. A school of female Bettas can be kept with one male safely.

Flowerhorn Cichlid

Aggressive fish species are often misunderstood. Some species are temperamental and show signs of aggression when they don’t have enough space around. The Flowerhorn cichlid is one such understood species. If you can give them the right water parameters and enough space, they often like to keep to themselves.

The nuchal hump over the tip of their nose is a distinguishing character. It is profoundly larger in the male species. They have a bright fuschia coloring on their body that is brighter around the top and fades away at the base.

They do put on quite a show when you interact with them. Also, the fish are aggressive, so find the right kind of tankmates for them. Typically, they do well in a larger tank with ample space.

Scientific Name Paraneetroplus synspilus
Common Name Golden monkey, Kamfa
Care Level Intermediate to advanced
Temperament Aggressive, Playful
Tank Size 70+ gallons

Bucktooth Tetra

You would think that tetras are pretty harmless in the tank, right? Well, Bucktooth tetra is an exception. Although moderate in size, these don’t perform that well in community tanks. So, if you are planning to house them, keep them in a same-species tank only.

The bucktooth tetra stands out with its appearance and has a silver-gray sheen on the body. Also, their body is semi-transparent, vividly visible under light. They are heavy fin nippers and even dig away into the scales of their tankmates.

However, they are shoaling fish. So, you can’t keep them alone in a tank. They often work well in groups of 10-12 typically. Also, they do have distinct water requirements, so keep up with the same accordingly.

Scientific Name Exodon paradoxus
Common Name Doesn’t have any
Care Level Intermediate
Temperament Semi-aggressive, Fin nippers
Tank Size 55+ gallons

Afer Knife

Just the name of this species sounds intimidating. However, Afer Knife is a favorite among several hobbyists. Native to certain parts of Africa, Afer Knife is commonly found in highly vegetated areas. Also, they are predators, so they keep alert for their next prey in the wild. Hence, the signs of aggression.

If you are housing them in your home aquarium, we’d recommend housing them in dimly lit tanks. They like to hide away in the plants, so decorate the tank accordingly. Make sure to add some driftwood as well. Also, due to their predatory behavior, they don’t fare well with other species.  So, house them in the same species tanks.

Scientific Name Papyrocranus afer
Common Name Marbled knifefish, Pom Pom knifefish
Care Level Intermediate to advanced
Temperament Predatory, Aggressive
Tank Size 150-200 gallons

Dwarf Pea Puffer

You wouldn’t think that a dwarf fish would be aggressive, but the Pea Puffer steals the show. Despite their small and cute appearance, their behavior is very misleading. They are pretty aggressive and heavy fin nippers too.

So, if you put them in a community tank, be assured of some fights. To keep the pea puffer and everyone at peace, house them in larger tanks. This provides them enough space to move around without obstruction. This also reduces territorial behavior.

The fish is native to India and lives in well-vegetated water bodies. So, mimicking the same in captivity is very much important. Due to their smaller size, they like to hide out under plants and rocks, so make sure your tank has enough of those.

Scientific Name Carinotetraodon travancoricus
Common Name Pygmy puffer, Pea puffer, Dwarf puffer
Care Level Intermediate
Temperament Aggressive, Territorial
Tank Size 20-30 gallons

Black Wolf Fish

Native to Amazon River Basic, the Black Wolffish is one you need to be aware of. Besides the sign of aggression, they are highly territorial and like their space. They have predatory behavior since they are the same in the wild.

It doesn’t do that great in community tanks due to its behavior. They also need warmer water temperatures to thrive. So, you need a water heater in case you live somewhere with a colder climate. The pH requirement is neutral so that it is easy to manage.

When growing them in captivity, you want to ensure that you feed them a carnivorous diet mainly. Insects, brined fish, and live fish work well in their diet. Just keep their diet protein-rich.

Scientific Name Hoplias curupira
Common Name Wolf fish
Care Level Intermediate
Temperament Predatory
Tank Size 120+ gallons

Convict Cichlid

We knew we had to include the Convict Cichlid in the list when it comes to aggressive fish species. This one is known for its notorious behavior and fierce temperament. Their appearance with the silver body and black stripes is a feast to the eye. However, that’s the only nice thing with them.

They look amazing under the aquarium light. They emit some colors under the light and even come off as iridescent. Although they have a terrible reputation, taking care of them isn’t as tricky.

If you provide them with enough space and take care of their water parameters, you should face many issues. They require larger tanks since they can get territorial. Also, adorn the tank with great decorations, including plants and rocks.

Scientific Name Amatitlania nigrofasciata
Common Name Zebra cichlid
Care Level Intermediate to advanced
Temperament Aggressive, Territorial
Tank Size 30-40 gallons

Severums

Another popular variant of Cichlids that is worth a mention is the Banded Cichlids. They are native to the Amazon region and have aggressive and predatory behavior.

Don’t get fooled by their cute appearance and unique design; they pose a threat to others. The male one can get pretty aggressive during mating season. So, if you want comfortable and healthy breeding, separate the mated fish to another tank.

However, one good thing about this species is that they are less aggressive compared to other cichlids. If they don’t feel pried or threatened, they will swim around and just keep to themselves.

Scientific Name Heros severus
Common Name Banded cichlid
Care Level Intermediate
Temperament Aggressive
Tank Size 55 gallons

Bichir

Although they are quite an underrated aquarium fish, Bichir was a must mention here. They are not just aggressive but highly territorial. The fish has a tapered body with a pointed mouth and base, much like an eel.

The fish has several triangular fins down their body. Also, one unique trait of this fish is their eyesight. They have terrible vision; hence they live to keep any other fish in close vicinity. Also, they need a sandy substrate for comfortable living. Don’t put sharp rocks or gravel in the bottom of the tank.

They don’t need any plants in their diet. They are 100% carnivores. So, although they aren’t predators, you can often find them nipping around the tank for food if they are hungry.

Scientific Name Polypterus mokelembembe
Common Name Bichir
Care Level Intermediate to advanced
Temperament Semi-aggressive
Tank Size 90-100 gallons

Silver Arowana

Silver Arowana shouldn’t be on your radar unless you are an expert and have years of experience handling fish. This is a quest for the aquarists, mainly because they are challenging to handle and care for.

The Silver Arowana has a unique banded appearance. The shape is slender and tapered around the ends. Their fin arrangement is also quite guided, so you’d have a hard time distinguishing the two.

Also, the fish has predatory tendencies. The hinging jaws are strong enough to bite into their prey and chomp them down for their feeding. So, if you are considering adding them to a community tank, we’d suggest being careful. The aggression levels in this fish are very unpredictable, which is one of the reasons why it is so hard to manage.

Scientific Name Osteoglossum bicirrhosum
Common Name Silver arowana, green arowana
Care Level Advanced
Temperament Aggressive, Predatory
Tank Size 250 gallons

Oscar Fish

It is not every day that you come across a fish that stands out in an aquarium. Well, Oscar fish is a showstopper. This is a type of Cichlid fish, so you need to know about the essential characteristics too.

They are trendy in the commercial fish trade. The fish has a base of black with splatters of bright red and orange all over. Despite their aggressive behavior, one good thing about these fish is that they are easy to care for. They are hardy and adapt pretty quickly.

Unlike most of the other carnivores, these are omnivores. So, you can give them a variety of foods, including frozen, dried, and even live foods. They can feed on veggies and fruits as treats.

Although Oscars aren’t very aggressive, they are big bullies. If they find smaller fish in their vicinity, they will drag them down. They can even gobble down smaller, vulnerable fish. So, be aware of that while choosing their tankmates.

Scientific Name Astronotus ocellatus
Common Name Oscar fish
Care Level Intermediate
Temperament Aggressive, Predatory, Bully
Tank Size 55 gallons

Jack Dempsey Fish

Although they have a unique name, their characteristics aren’t that pleasing. They are rightfully named after a boxer if their bullying tendencies are anything to go by.

However, if you house them in a single tank and want to interact with them, they are pretty nice to build a relationship or connection with. This fish is quite hardy and can live in hotter water temperatures. This makes them immune to sudden water changes.

As for their appearance, Jack Dempsey is a spotted fish. It has a range of black, blue, and even purple spots littered all across its body. The face has a stout look to it. Also, their facial muscles are substantial and strong.

The fish is aggressive, hence in the list, duh! However, with proper care and a large open capacity in the tank, you shouldn’t have any issues. They don’t like overcrowded tanks, so keep the decorations to a minimum.

Scientific Name Rocio octofasciata
Common Name Jack Dempsey fish
Care Level Intermediate
Temperament Aggressive
Tank Size 55 gallons

Mini Dovii

Finding rare fish in the aquarium trade is not that difficult. And Mini Dovii often makes it to the top of the list. They are a type of Cichlid, but they are comparatively a lot well-behaved.

The fish has a darker base color with bright red dots all over. They are designed to perfection with a linear arrangement of dots all over their body.

Although they are not very aggressive, the most common issue with them is that they are territorial. You need to provide them with enough space; otherwise, they will start a fight in the tank. The best way to deter them is by hiding the other fish with decorations. So, fill up the tank accordingly.

Scientific Name Chiapaheros grammodes
Common Name Sieve cichlid
Care Level Intermediate
Temperament Territorial
Tank Size 75 gallons

Poor Man’s Tropheus

Sometimes, big bangs come in small packages. The Poor Man’s Tropheus is a testament to that. Although they hardly grow up to 5.5 inches, the fish is highly aggressive.

They like to keep in pairs and stay with their partners for a comfortable life. If you try to introduce them to a community tank, they need to have their own space. The coloration on the Poor Man’s Tropheus’s body isn’t very prominent. They have a dull appearance, but they are pretty interactive.

One unique trait to them is that they change color during breeding. Typically, they perform better in the same species tanks, so stick to that in the beginning. Also, if your aquarium has caves and plants, they will mark their territory around it.

Scientific Name Hypsophrys nematopus
Common Name Green-eyed cichlid
Care Level Intermediate
Temperament Territorial
Tank Size 30 gallons

Gourami

You might sit here and think, “Aren’t these peaceful?”

Well, technically, they are. However, their behavior can soon turn a complete 360 if things aren’t in their favor. The worst part of this fish is that it doesn’t do well with its kind. So, while it will stay peacefully with other fish species, gouramis are territorial with their kind.

However, adding gourami to an aquarium is a fun experience. They are brilliant creatures and are fun to interact with.

You need to be very careful about the tank mates since they like to keep their calm around only a handful of species. They do well with neon tetras, guppies, etc.

Scientific Name Osphronemidae
Common Name Bettas, giant and dwarf gouramis
Care Level Easy to intermediate
Temperament Territorial
Tank Size Starts with 10 gallons

Black Piranha

While we are on the topic of discussing aggressive fish, there is no way we can miss out on Black Piranha. These are the OG carnivorous fish everyone knows of.

The black variants aren’t commonly used in the aquarium trade. It is the red-bellied version that everyone buys for their fish tanks. However, the black piranhas are very predatory and risky. You need to proceed with caution when it comes to black piranhas. Not only are they a threat to their tankmates, but they are also a threat to you.

So, if you are trying to hand feed them, don’t. They are aggressive and can break through the filters and plastic tubing in the tank. We’d not recommend housing a piranha of any kind in the house.

Scientific Name Serrasalmus rhombeus
Common Name Black piranha
Care Level Advanced
Temperament Very aggressive
Tank Size 180+ gallons

Red Terror Cichlid

If you want a pretty newly found cichlid species in your tank, the red terror cichlids are the perfect one. They can grow up to 20 inches, which is terrifying.

So, if you have a larger tank or space, only then should you consider getting it. The bright colors with a mix of orange, yellow, and black make it stand out in the tank. The males have an expanded fin with blur spangles, which is always a benefit.

They are fin nippers and will bite on your hand too when you are changing their water. So, if you don’t practice caution, you risk hurting yourself in the process. They are hardy but not very adaptable, so you can’t move them around a lot.

Scientific Name Mesoheros festae
Common Name Red terror
Care Level Intermediate to advanced
Temperament Aggressive
Tank Size 150 gallons

Snakehead

As intimidating as the name of the fish is, Snakehead itself is quite a domination species. It is native to America and is very rarely found. They are dangerous and invasive fish, which is why you need to handle them with extra caution.

Snakeheads don’t enjoy human interaction. So, if you are housing them in a fish tank hoping to interact with them, they won’t. They like to hide away under the plants and caves.

Since they are very protective parents, you will find the snakeheads become more aggressive during the breeding season. We’d recommend separating the male and female into a breeding tank to minimize risks or injuries.

Scientific Name Channidae
Common Name Snakehead
Care Level Intermediate to advanced
Temperament Aggressive, dangerous
Tank Size 110+ gallons

Freshwater Stingray

Although not a common choice for home aquariums, stingrays were still worth a mention. This is because there are enthusiasts that like to house stingrays in their home aquariums.

They are pleasant to look at, and they are interactive too. However, they don’t perform well in community tanks. If you keep them in smaller and congested tanks, that’s when they become aggressive.

Stingrays like their space. So, if they find something else obstructing that, they will get picky and start showing signs of dominance. They also bully vulnerable fish in the tank with fin nipping tendencies.

Scientific Name Myliobatoidei
Common Name Stingray
Care Level Intermediate to advanced
Temperament Semi-aggressive, territorial
Tank Size 150+ gallons

Green Terror Cichlid

Bright-colored fish species spruce up the look of a tank, and the green terror cichlid is one such species. However, they come with their downsides too. Not only are they aggressive, but they can also get into bullying smaller fish in the tank.

Although you will find green terror in community tanks, they need to be kept under caution. They have a habit of eating their tankmates, so keep your eyes open about that.

One unique trait of this fish is that they form bonded pairs. This doubles their power and their aggression too. So, if you have vulnerable fish in the tank that could be under threat, remove them immediately.

Scientific Name Andinoacara rivulatus
Common Name Green terror cichlid
Care Level Intermediate
Temperament Aggressive
Tank Size 30-40 gallons

Freshwater Pufferfish

Although we have mentioned one kind of pufferfish in the list, the standard one deserved mention too. The freshwater pufferfish are pretty harmless. However, things don’t always happen the way they look on the surface.

The fish is unique in its anatomy and physiology, especially when you pull it out of the tank. However, they have their set of defense mechanisms too. The hard beak can easily take chunks out of other fish.

If they feel threatened or hungry, they will show signs of aggression and start nipping on the flesh of other fish in the tank. So, make sure you feed them on time and without any delay.

Scientific Name Tetraodon lineatus
Common Name Pufferfish
Care Level Intermediate
Temperament Peaceful to mild aggression
Tank Size 30 gallons minimum

Kenyi Cichlid

Last but not least is the Kenyi cichlid. Given that there are so many different types of cichlid, this one is quite a rare find. It is native to Lake Malawi and has a bright color to its appearance. The vibrant blue color with stripes all over makes it stand out from the crowd in the tank.

The males are territorial and can get pretty aggressive as they mature. Also, they are pretty fast swimmers and zoom around the tank without any stop. The biggest issue with this species is that they attack when they feel threatened. So, even if the other fish isn’t doing anything, the Kenyi will attack them if they feel threatened.

Scientific Name Maylandia lombardoi
Common Name Kenyi cichlid
Care Level Easy to intermediate
Temperament Peaceful, territorial
Tank Size 15-20 gallons minimum

The Environment Dictates the Rules

The many types of fish labeled as aggressive are due to research and fishkeeping experience.

It is very important to be informed about the types of fish categorized as aggressive and how to avoid bad situations if you keep any of these species.

Creating the optimal environment such as space and complementary tank mates can create balance even within a tank filled with aggressive predators.

What’s your experience with aggressive freshwater fish? Comment and share with us.

21 thoughts on “Aggressive Freshwater Fish”

  1. Unfortunately, I bought a CAE ( Chinese Algae Eater ), never thought it will be aggressive when it become old. I am planning to separate it from the rest of my fishes!

    Reply
    • Yes Chinese algae eaters are very aggressive and can live with oscars, convicts, frontosa, red devil Cichlids, Texas Cichlids, you name it. When they get big they are very tough and mean fish that will kill non aggressive tank mates and eat them. They are catfish.

      Reply
  2. I’m planning to get fish that will be kept in the same tank. This really helped me, I was thinking of getting two tiger barbs. But maybe not any more….

    Reply
  3. Hi what’s the meanest thing I can get for my tank? piranhas r pretty boring been looking at snakeheads. Want something that won’t let me put my hand in the tank.

    Reply
    • Jaguar cichlids are ment to be pretty aggressive, feed them blood worm I did with my angel fish and every time I stuck my hand in they would nip my hand

      Reply
  4. I have a male betta in a 5 gal tank he has white onhis nose and under chin area.i took him out of a 36 gal tank as he was being nipped at by tetras

    Reply
  5. Putting a tank together 55 gallon. I want aggressive fish that can be in the same tank. My last tank the red devil killed everything including green terror Jack Dempsey convict and a few others. What’s OK to out in with an aggressive red devil?

    Reply
    • Hey Dave! It depends weather it is a female or a male. Females can live with members of their on species but males can not. Other south american cichlids could be good too!

      Reply
  6. Cichlids are actually not aggressive when put with the right other fish! You have to know what is right for your fish. This also goes for tiger barbs, they are amazing fish for a 6-9 on aggressiveness in your tank (10 being really aggressive). I am 13 and have had a school of tiger barbs in my tank for around 2 years now and they are fine! I have a rating of 7 on aggressiveness in my tank. If you can’t do cichlids or tiger barbs, cherry barbs is a great way to go too!

    Reply
    • I have two Oscar fish I had 2 angel fish 2 coys 2 white tetras and 2 cichlids and my Oscar fish ate them or rammed into them and killed them all what fish can I put with Oscars

      Reply

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