25 Aggressive Freshwater Fish for Predator Tanks (Species Guide)

Aggressive fish present a unique tank dynamic, something that can’t be replicated by the interactions between peaceful fish.

The way that they behave with one another is alluring to many fish keepers, and their behavior is one of the primary reasons to keep them.

They also tend to be highly intelligent, and most can form bonds with their owners, while most peaceful fish cannot.

In this guide, we will cover 20 common (and not so common) types of aggressive fish that you can keep at home!

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25 Aggressive Freshwater Fish

Here are a few of our favorite species of aggressive freshwater fish:

1. Wolf Cichlid

• Scientific Name: Parachromis dovii
• Common Name: Wolf Cichild, Rainbow Bass, Dovii
• Care Level: Advanced
• Temperament: Aggressive
• Tank Size: Juvenile: 130 gallons, Adult: Large custom aquarium, at least 4-6x the length of the fish.

The Wolf Cichlid is an infamous fish purely due to its highly aggressive nature. While they are gorgeous and extremely intelligent, their temperament is unique to the point that “dovii” has become synonymous with aggression.

Tank mates are hit or miss, normally miss. If it is a hit, it normally does not last long, as Wolf Cichlids grow very large very quickly, eventually reaching over two feet in size. Most keepers either move them to large ponds, or order custom-built tanks to house their Dovii in.

While they are still juveniles, you may have some success keeping them with other similarly sized, aggressive cichlids. Their tank should have a deep sand bed, rocks, caves, as well as large open swimming spaces. Wolf cichlids like to have some caves and rocks to hide in/among, as they can get startled despite their aggressive nature. In addition, Wolf Cichlids show strong interest in activity beyond the walls of the tank and may even consider some of the outside room a part of their territory.

2. Red Devil Cichlid

• Scientific Name: Amphilophus labiatus
• Common Name: Red Devil, Red Devil Cichlid
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 75 gallons

Red Devils are aptly named for their aggressive nature, and similar to the Dovii, keeping them with tankmates is only recommended while they are still juveniles. However, some have had success by setting up various large “caves” in the aquarium. This allows the adult Red Devil to establish a territory, and as long as other fish stay away from it, they are generally, though not always, left alone.

The Red Devil ranges in coloration from fish to fish, and despite their name, they may appear fully yellow, pale white, or even orange, though most do have some red coloration. They are not picky eaters, and as long as you provide them with rocks, caves, and appropriately sized tank, proper water parameters, and food, they will live similar lifespans to dogs.

3. Jaguar Cichlid

• Scientific Name: Parachromis managuensis
• Common Name: Jaguar Cichlid, Managuense Cichlid
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 125 gallons for juvenile, adult needs 240+ gallons

The fantastically patterned jaguar cichlid is a wholly underrated fish. They have a light cream to yellow body with brilliant black patterning, similar to a jaguar. In addition, their patterning will shift and change as they grow, only solidifying once they are fully mature, which makes their growth much more interesting than other cichlids.

Jaguar Cichlids should also be provided with rocks, caves, and substrate they can dig in. They can be housed with other fish, mostly cichlids of similar size and aggression levels, as they will still attempt to eat any fish smaller than themselves.

However, housing multiple Jaguar Cichlids together can be quite tricky, as they will kill others of both their own and the opposite sex. Unless they were raised together, you will likely be unsuccessful in keeping more than one together.

4. Umbee Cichild

• Scientific Name: Caquetaia Umbriferus
• Common Name: Umbee, Umbee Cichlid, Blue-freckled Cichlid, Turquoise Cichlid
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 100+ for juvenile, 240+ gallons for adult

A rival to the Dovii Cichlid in terms of coloration, aggression, and personality, the Umbee is another highly aggressive and highly interactive cichlid. Both of these fish show a strong interest in happenings outside of their tank, which demonstrates their high levels of intelligence, and is a great plus in owning either species.

It is not recommended to keep them with tankmates, though some have had success keeping them with large sailfin plecos and retail catfish, though if the catfish grow faster than the Umbee, your Umbee will be a snack. Umbee cichlids are not picky eaters, and if you can handle their aggression and other requirements, they are not difficult to care for.

They get slightly smaller than Dovii, so a large custom tank or pond would be required long term, but their high levels of interactivity and personality are worth the investment. They live longer than the average dog, but have just as much, if not more, personality.

5. Jewel Cichlid

• Scientific Name: Hemichromis
• Common Name: Jewel Cichlid
• Care Level: Beginner-Intermediate
• Temperament: Aggressive
• Tank Size: 40-100 gallons, depending on species

The Jewel Cichlid, aptly named for its beautiful coloration, is often the primary attraction of whatever tank it inhabits. This fish’s aggression is only based around its territory, so if it has enough room and a particular object to establish a territory around, it can be successfully kept with other fish.

However, you should bear in mind that this fish will eat any fish smaller than itself. If you were hoping to have this fish as a lovely centerpiece with neon tetras, rosy red minnows, and other such fish, this is unfortunately impossible. Other large cichlids are the best tankmates for them, though it is best to raise them together as juveniles, as Jewel Cichlids may attack unfamiliar fish.

6. Mini Dovii

• Scientific Name: Cichlasoma grammodes
• Common Name: Mini Dovii, Grammodes
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 125+ gallons

The Mini Dovii only reaches about half the size of a real Dovii and is not a closely related species. Despite this, they are extremely aggressive and will attempt to kill off anything else in the tank, though some have successfully kept pairs together.

They are less interested in the outside environment of their tank than Wolf Cichilds but are still quite gorgeous and personable. They have that gritty aggressive nature that some keepers long for and are able to successfully be kept with others of their own kind, which is much rarer for the Wolf Cichlid. Mini Dovii’s are very slow growers, so if you plan on keeping a fish you can slowly graduate to larger tanks, this species is a great choice.

7. Flowerhorn

• Scientific Name: Unknown/Not Yet Established
• Common Name: Flowerhorn
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 40-75+ gallons, depending on type

The Flowerhorn Cichlid is an unknown hybrid of many different cichlids, and while they vary widely in size, coloration, and body type, they are all known to be aggressive. Some keepers prefer to house them alone, especially because they are incredibly interactive fish, and one of the only fish who actively look to be petted.

They come in a wide variety of colors and dispositions, though all are aggressive. Some are able to be housed with other large cichlids, some get along with catfish, and some do not get along with any other fish, period. Given that they were bred purely for color and interactive personalities, they are one of the absolute best pet fish one can own. Flowerhorns are not picky eaters, and while they prefer tanks with decorations, they will become more interactive if they are deprived of stimulations like decorations.

8. Oscar Fish

• Scientific Name: Astronotus ocellatus
• Common Name: Oscar, Oscar Cichlid
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 75-125 gallons

The Oscar fish is a common, yet highly territorial, fish found in nearly every pet store. They can reach over a foot in length and come in a beautiful array of colors, and despite their mean looking faces and bad attitude towards other fish, they are absolute sweeties to their owners.

It is recommended to house Oscars alone, but it is more than possible to keep them with other large fish. They do best with other cichlids, bichirs, large catfish, and large schooling fish, such as the Silver Dollar. Oscars are only semi aggressive, so tankmates are much more doable than some of the other fish on this list. Most people who own them describe them as “puppy dogs” and other such pet names, as they truly bond with their owner and offer a lot of interactivity.

9. Black Wolffish

• Scientific Name: Hoplias Curupira
• Common Name: Black Wolf, Wolffish, Black Wolf Fish, Curupira
• Care Level: Advanced
• Temperament: Aggressive
• Tank Size: Large custom tank, at least 5ft long, 3ft wide, preferably over 200 gallons

The Black Wolffish is an aggressive predator originating from the Amazon basin. They have an impressive array of teeth and body shape and cannot be mistaken for anything except for a predator. They max out at a little over a foot in length, and despite their ferocious appearance, they have successfully been kept in community tanks.

Some keepers have had success keeping this fish with bichirs, silver dollars, peacock bass cichlids, and other fast-moving large fish. Wolffish are not cheap, and they are not common, and while this can be a downer to some, it practically guarantees that this fish will go to someone with the appropriate means to care for it.

10. Hoplias Aimara

• Scientific Name: Hoplias Aimara
• Common Name: Wolffish, Black Wolffish, Aimara
• Care Level: Advanced
• Temperament: Aggressive
• Tank Size: Large custom tank, similar to Curupira

Don’t worry, we didn’t list the same fish twice. This is a close relative of the previous black wolf fish, with a few major differences. The Aimara is less frequently found, often quite more expensive (averaging $800, though several thousand dollars is not uncommon), and exclusively kept by those searching for large, predatory fish.

Aimara tend to be much more aggressive than Curupir, and while some have had success keeping Curupir with tank mates, it is not at all recommended to keep Aimara with any tankmates. However, this could be because only aggressive tankmates would stand a chance, and no one wants to risk a fish they paid $800-$3000 for simply to have an extra fish in the tank.

Aimara are aggressive predators and tend to be hearty eaters. They have been known to act aggressively not just towards other fish, but also towards their owners. Aimara, and most Wolffish, are not kept to be “pet” fish, but rather are kept to experience this predator up close.

11. Green Texas Cichlid

• Scientific Name: Herichthys cyanoguttatus
• Common Name: Green Texas Cichlid, Texas Cichlid, Pearlscale Cichlid
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 55 gallons

The Green Texas Cichlid is a gorgeous and iridescent fish fully capable of capturing their owner’s heart. They are highly interactive and intelligent, and their only downside is their aggression. If you attempt to house them with anything that doesn’t have an equal or higher aggression level, your Texas Cichlid will kill it.

These fish appreciate dimly lit tanks, roots (or decorations that mimic roots), floating plants, and caves. In addition, this setup is perfect for other fish you can house with your Texas cichlid, such as similarly sized Central and South American Cichlids.

You can also keep one by itself, though it is more common to house them with other cichlids. If you keep them by themselves, they will interact with you more and will require more stimulation from the tank environment. Keep in mind that once you start keeping a Green Texas Cichlid by itself, it will be extremely difficult to reintroduce other fish into the tank.

12. Poor Man’s Tropheus

• Scientific Name: Hypsophrys nematopus
• Common Name: Poor Man’s Tropheus, Green-eyed Cichlid
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 30 gallons

While this fish may be smaller than many of the others on this list, they are highly aggressive and will kill fish larger than themselves. They are not particularly colorful, but if you happen to end up with a male/female pair, their color change during breeding more than makes up for it. As they are, they aren’t bad looking, just not as colorful as some of the other aggressive options.

Some keepers have had success housing them with other fish, though most elect to keep them by themselves, with either a single specimen, a pair, or a small group. They will become territorial around certain caves and other decorations, and by providing territories for them to defend, you can lessen their overall aggression.

13. Afer Knife

• Scientific Name: Papyrocranus afer
• Common Name: Afer Knife, Pom Pom Knife, Reticulated Knifefish
• Care Level: Advanced
• Temperament: Aggressive
• Tank Size: Large custom tank or pond, at least 200 gallons, depending on dimensions.

While most Knifefish are known for being extremely shy and spending most of their time hiding, the aggressive Afer Knife breaks that mold. They still require many hiding areas in the tank but are well known for attacking their tankmates.

Many keepers are able to successfully house them with other fish while they are juveniles, but as they grow, they become more aggressive and territorial. Once they hit this stage, they either need to be kept alone, or kept with other large and aggressive fish, though there is still a chance of them attacking other fish.

The fish they take a disliking to seems to vary from individual to individual, with some being fine with large cichlids and arowanas, while others will attack those species without hesitation. All Afer Knives seem to be particularly aggressive towards other knifefish and cannot be housed with similar species.

14. Gourami

• Scientific Name: Osphronemidae
• Common Name: Gourami, includes dwarf gourami, giant gourami, bettas
• Care Level: Beginner to Advanced
• Temperament: Semi Aggressive
• Tank Size: 5-220 gallons, depending on species

The famous betta is well known for its aggression, as are most other gourami. While most Gouramis are actually pretty peaceful in community aquariums, they generally don’t get along well with other Gourami.

These fish are personable and intelligent, and can normally distinguish between gourami and other fish, and can be peacefully kept with appropriate tank mates.

For example, a gourami is very unlikely to attack harlequin rasboras, neon tetras, or similar fish, but some, particularly bettas, may attack very colorful fish like guppies.

15. Peacock Bass Cichlid

• Scientific Name: Cichla ocellaris
• Common Name: Peacock Bass, Peacock Cichlid, Peacock Bass Cichlid
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 220+ gallons

This impressively colored and aggressive cichlid is not for the faint of heart. They reach over two feet in length, requiring specialized tanks or ponds, and do not play well with less aggressive species. Peacock Cichlids are stunning, presenting a yellow to tan body, black stripes and patterns, and red fins. They also have a very distinctive eye spot on the beginning of their tail.

For any monster fish keepers, these are a must. They closely resemble largemouth bass, despite the fact that they are not bass at all, and look stunning, both at their juvenile and fully-grown stages. Just by looking at this fish, you can clearly see that it was made to be a predator.

When they are young, you can house them with similarly sized aggressive cichlids, but as they grow, you will have to separate them before the peacock bass cichlid outgrows its “friends”. As adults, some have had success keeping them with others of their own kind, other large and aggressive cichlids, arowanas, and large catfish.

16. Pea Puffer

• Scientific Name: Carinotetraodon travancoricus
• Common Name: Pea Puffer, BB Puffer, Malabar Puffer, Pygmy Puffer
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 5 gallons for one, 15 for up to three

While they are the smallest fish on this list, and one of the smallest fish in general, the pea puffer should not be underestimated. Despite the fact that they only reach an inch in size, they can take out much larger fish and should only be kept with others of their own kind.

Occasionally people will try and keep them in community tanks, and for a while, it will work. Then some smaller tetras and other fish will start randomly dying, their larger fish will have noticeably missing flesh, and the fins of all the fish will be ragged and have chunks missing.

Pea puffers are territorial, and they don’t like other fish. If they can’t kill them outright, they will start taking small chunks out of the fish until it leaves their territory, but in aquariums, this isn’t possible. Despite their small size, their aggressive nature is unmistakable.

17. Jack Dempsey

• Scientific Name: Rocio octofasciata
• Common Name: Jack Dempsey Cichlid
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 55 gallons

Jack Dempseys are popular for their appearance and personality. Their bodies are darkly striated with hundreds of brilliantly iridescent scales, almost giving the appearance of galaxies. Like most cichlids, the Jack Dempsey is intelligent and will interact with its owner, but it is also quite aggressive.

Luckily, many fish keepers have had success housing them with other species. They do best with other large, similarly aggressive cichlids. Your Jack Dempsey will need various caves and hiding areas, whether they are housed alone or with other fish. They are not notably difficult to care for, aside from their obvious aggression, so they can be a good starter for anyone looking for their first aggressive fish.

18. Arowana

• Scientific Name: Osteoglossidae
• Common Name: Arowana, Dragon Fish, Dragonfish
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 200-300+ gallons, depending on species

One of the kings of the aquarium, arowanas are well known in the fish keeping world. They have sleek, streamlined bodies and highly reflective scales, and if you’re not in the US, they come in a massive array of colors, with some of these colors selling for well over $100,000.

These fish are associated with luck and good fortune in some Asian cultures, which has caused excessive numbers to be removed from the wild. Legend has it that if the owner of this fish falls ill, the fish will take on the sickness to save its owner. Similarly, the fish will die in the place of the owner, giving the owner another chance at life.

Arowanas are top dwelling predators and highly active, which makes them unique to watch. They move gracefully, unlike any other fish, and can be housed with several other species. However, since these other species have to be somewhat aggressive to defend against the arowana, most keepers do not risk their highly valued fish, and instead house them alone in spacious tanks.

19. Severums

• Scientific Name: Heros severus
• Common Name: Banded Cichlid, Green Severum, Tiger Severum
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 55 gallons

Severums are a peculiar looking fish with large round eyes and an overall rounded body, similar to the discus, though these are a fair bit more aggressive. Even though their eyes and tiny mouths make them look absolutely adorable, they will kill their tankmates if you’re not careful.

Severums prefer tanks that are decorated with driftwood and rocks, and while a substrate is not necessary, they like to pick through sand substrates. If you house them with cichlids of a similar size and temperament, you will have a perfectly functional tank. However, if you try to put fish that are smaller than your Severum into its tank, well, that fish won’t be around much longer. In addition, if you attempt to house them with any tankmates in a small tank, the Severum will attack and kill them.

20. Ornate bichir

• Scientific Name: Polypterus ornatipinnis
• Common Name: Ornate bichir, Dragon eel
• Care Level: Intermediate
• Temperament: Aggressive
• Tank Size: 180 gallons

While most bichirs are peaceful with the occasional mean streak, the ornate bichir is arguably the most aggressive. They can normally coexist with mid-level and upper-level large tankmates, but if they are housed with small, bottom-dwelling, or similar looking species, they will attack them.

Some keepers have also noticed their ornate bichirs going after the tails of other fish, so if you are suddenly finding fish with ragged tails, you should keep a close eye on your bichir. They do not seem to have a preference for species only or community tanks, as they tend to primarily ignore other fish in community tanks. How you house them is up to you, but you should be cautious when selecting tankmates.

21.) Convict Cichlid

• Scientific Name: Amatitlania nigrofasciata
• Common Name: Convict Cichlid
• Care Level: Beginner
• Temperament: Aggressive
• Tank Size: 20+ Gallons

Convict Cichlids are a true staple of the aquarium hobby and are often people’s first dip into the exciting world of cichlids. Being so small (4-5 inches maximum), affordable, and attractive, they fit nicely into smaller community tanks. At first, that is…

Unfortunately, many aquarists quickly discover that these cichlids are incredibly feisty for their size. Convict Cichlids are very willing to take on tank mates twice their size in lip locking contests for dominance. Convicts will also bully or even kill smaller tank mates if the tank isn’t spacious enough for them to claim a territory of their own.

And when breeding they become positively vicious and will crowd every other fish in the tank to the upper corners with biting and chasing. A single pair of breeding Convicts can live comfortably in 10 gallons of space. But you’ll want at least a 20 gallon tank if keeping one in a community. And 55 gallons or more for a breeding pair with tank mates!

Like most Central American cichlids they prefer hard, alkaline water chemistry (pH 7.0+) and tropical temperatures of 74℉ or higher. They are also avid diggers, building mounds and pits in the substrate constantly. If your Convicts do decide to spawn, you can say goodbye to any rooted plants!

22.) Black Piranha

• Scientific Name: Serrasalmus rhombeus
• Common Name: Black Piranha, White Piranha
• Care Level: Expert
• Temperament: Aggressive; Dangerous
• Tank Size: 180+ gallons

Red Bellied Piranhas are the species you commonly see in the trade but the second most common is also the more aggressive of the two. Red Bellies tend to be skittish, schooling fish but Black Piranhas are solitary predators that reach 16-20 inches in length when fully grown.

Black Piranhas are rated as Dangerous because they are fully capable of causing harm to you as well as their tank mates. They will aggressively attack anything that invades their territory, which is the entire tank once they are fully grown. Cleaning a Black Piranha tank can be a challenge when they get large enough to break plastic vacuum tubes and algae scrubbing pads. That said, you can often keep them with tiny fish like Guppies and Tetras since they are too small to be worth chasing down. So long as the Black Piranha is well fed at all times.

23.) Red Tailed Shark

• Scientific Name: Epalzeorhynchos bicolor
• Common Name: Red Tailed Shark, Red Tail Black Shark
• Care Level: Beginner
• Temperament: Semi-aggressive; Territorial
• Tank Size: 30 Gallons

Red Tailed Sharks aren’t true sharks at all; in fact, they are Cyprinids and thus closely related to Barbs, Goldfish, and Danios! However they are not at all like their relatives when it comes to personality. Rather than being gentle schooling fish, Red Tailed Sharks (as well as Rainbow and Black Sharks) are solitary, territorial bottom dwellers. 

Keeping them with others of their own kind is a recipe for trouble because they will fight constantly. And they can give their tank mates trouble if not given a cave, driftwood tangle, or other place to defend along the bottom. Red Tailed Sharks may claim the entire bottom of the tank as their turf, chasing anything that dares swim in that zone.

While occasionally mean, when given a place of their own Red Tail Sharks are good community fish alongside semi-aggressive to aggressive fish. They are omnivorous and eat not only flakes and frozen food but algae and other soft greens as well!

24.) Bucktoothed Tetra

• Scientific Name: Exodon paradoxus
• Common Name: Bucktoothed Tetra, Clown Tetra
• Care Level: Beginner-Intermediate
• Temperament: Semi-aggressive; Schooling
• Tank Size: 30 gallons

Bucktoothed Tetras show up occasionally at local pet stores, which is unfortunate because they aren’t very well suited for the majority of community tanks. They can grow to be 5-6 inches long and are large enough to pick smaller fish to pieces, including Guppies and Neon Tetras. They are also infamous for their scale-eating habits, smashing their specialized teeth against larger fish at high speeds to knock loose clouds of scales to eat.

Aggressive tank mates may be able to keep them at bay but Bucktoothed Tetras will descale and kill more peaceful tank mates. Keeping them with medium sized, scaleless fish like many predatory catfish is the best way to ensure everyone gets along. Otherwise, Bucktoothed Tetras are easy to care for, hardy, and offer an intriguing alternative as a medium sized dither fish!

They enjoy the same conditions as most other Amazonian natives: soft, acidic water chemistry (pH 5.5-7.0) and elevated tropical temperatures of 75-82℉. And remember that Bucktoothed Tetras are carnivorous so supplement any prepared foods with brine shrimp, bloodworms, and other meaty invertebrates!

25.) Red Terror Cichlid

• Scientific Name: Mesoheros festae
• Common Name: Red Terror
• Care Level: Intermediate-Expert
• Temperament: Aggressive
• Tank Size: 150+ gallons

The Red Terror is one of the largest New World cichlids found in the hobby; only the Umbee Cichlid, Wolf Cichlid, and a few others are larger. Adult male Red Terrors reach up to 20 inches in length, while females “only” grow to 15 inches. Both are intensely colorful as well. When spawning both fish have brilliant red and orange tones with vibrant black stripes, like an overgrown Convict Cichlid. The male also has extended fins and blur spangles while the female tends to be a deeper orangey-red color.

At this point, every other fish in the tank needs to be removed because Red Terrors are viciously defensive parents. They will kill anything that can’t escape the tank and will even nip at hands and fingers! So long as you can provide for their size and tempers they are hardy fish and some of the most beautiful New World cichlids out there.

Aquascaping for Red Terrors is a challenge because they will shift around the substrate to meet their needs. But you may have luck using epiphytic plants like Anubias and Java Fern. Epiphytes are plants that attach directly to hard surfaces and don’t need to be rooted in sand or gravel!