If you are planning to add more fish to your aquarium, it is important to know which breeds are particularly aggressive.

This will help you to avoid ones that are unlikely to get along with the fish you already have. Learning about these fish can save you a great deal of expense and frustration.

10 Most Aggressive Freshwater Fish

1. Arowana

Arowana 1

The arowana or Silver & Asian fish is definitely among the most aggressive fishes on the planet. They are also pretty high maintenance, which is why so many people are reluctant to get them in the first place.

A Silver Arowana can easily reach a size of three feet in length with a maximum weight of ten pounds. This means that you will need to have a minimum 250-gallon aquarium. If you don’t already have an aquarium this size, buying one is pretty expensive.

2. Wolf Cichlid

wolf cichlid

The Wolf Cichlid is another very aggressive fish, but it is also known for its staggering intelligence. These fish grow at a rapid rate and require a tank that is at least 130 gallons by the time they are fully matured adults.

While it is fairly easy to keep these fish while they are still young, they grow up before you know it. You should have plenty of rocks and other things that allow them to hide in their aquarium.

3. Piranha

red piranha

Most people are familiar with Piranhas, as they have a reputation for being particularly vicious. There are many different species of this carnivorous fish, some of which are more or less aggressive than others.

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This fish’s roots can be traced back to South America, specifically the Amazon River. If you plan on getting juvenile Piranha, you will need at least a 20-gallon tank, which isn’t ridiculous. 

4. Jaguar Cichlid

Jaguar Cichlid

The Jaguar Cichlid is often overlooked as a pet, but it does have a lot to offer. This fish has a unique black pattern on it, hence the name. This pattern changes as the fish develops and gets older. It becomes solid once it is a mature adult.

It is important to keep plenty of caves, rocks and other things in the aquarium if you have this type of cichlid. You’ll want to avoid keeping it with others of its own kind, as this usually leads to some pretty violent behavior.

5. Mini Dovii

The Mini Dovii is a highly aggressive fish that basically doesn’t get along with any other fish, so you have to keep it in its own tank. You will need to get an aquarium that is at least 125 gallons, but preferably more. 

These fish don’t have much interest in anything outside of its aquarium. They can be difficult to care for but aren’t quite as high-maintenance as some other species.

6. Flowerhorn


The Flowerhorn Cichlid is an excellent fish for beginners, but it is quite aggressive. You’ll want to get a 40 to 75 gallon tank, depending on which type you want. You may be able to keep it with other Cichlids, but it’s always a bit of a gamble.

One of the great things about these fish is that they love to interact with their outside environment. This can make for some really amusing and entertaining moments.

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7. Pignose Puffer Fish

When you are searching for an aggressive fish, the Pig Nose Puffer is one to consider. It exhibits aggressive behavior when a new tank mate is introduced to the aquarium. A bluff charge is executed in order to see if the other fish is intimated.

You will need at least a 70 gallon tank for this fish. It should resemble its natural environment as closely as possible. They are carnivorous fish, which means that you can give them anything from shrimp to various small fish.

8. Rainbow Shark

Rainbow Shark 1

The Rainbow Shark is an interesting freshwater fish that has a serious attitude. While it may not actually be a shark at all, this fish is fairly aggressive. It is the erect dorsal fin that has earned this fish its name.

When this fish reaches full maturity, you will see just how aggressive it can be. This is especially true if you have any other fish in the tank with it. Just make sure that whatever you put in the aquarium can hold its own. Some of the best fish for tank mates include Barbs, Danios, and Rainbowfish.

9. Red-Tailed Shark

Red Tailed Shark

The Red Tailed Shark is also not a true shark, though it does sort of resemble one. These fish are mostly black with a reddish-orange tail. They are actually a bit shy when they are still juveniles, but they quickly become much bolder.

Some of the best food for this non-shark fish includes fruits, bloodworms, and shrimp. It is known for its territoriality and aggression. While this fish probably won’t nip at the other fish in your tank, it will chase them around a lot.

10. Tiger Barb

Tiger Barb

The Tiger Barb is a small but aggressive fish that doesn’t get along very well with most other fish. It does, however, have a beautiful orange coloration with black stripes going down its body. You can keep five or six of these fish together without any issues. They also get along well with Platys and Catfish.

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  • The Arowana fish grows up to three feet and is highly aggressive, so it is not a good choice for novices.
  • The Wolf Cichlid grows very quickly and is easy to keep until it starts to mature.
  • Piranhas are carnivorous fish that are naturally found in the Amazon River.
  • The Jaguar Cichlid makes for a great pet, but you don’t want to keep it with others of the same sub-species.
  • The Mini Dovii is very territorial but focuses mostly on the inside of its own aquarium, ignoring the outside world entirely.
  • Flowerhorns are great fish for non-experienced owners, and they love to interact with the world outside of their tank.
  • The Pig Nose Puffer Fish will charge at a new addition to their aquarium, but they are pretty harmless overall.
  • The Rainbow Shark is not an actual shark, but it does become very aggressive when it reaches fully maturity.
  • The Red Tailed Shark is also a non-shark that can be skittish when it is young, but it becomes bold as it ages.
  • The Tiger Barb doesn’t get along well with most other fish, and it is not for beginners.

We do miss images for the Pignose Pufferfish & the Mini Dovii. Do you have them in your aquarium and know how to take good images? We will buy them from you! Just send a message in our contact form!

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Hi! I'm Anna and I´m a certified cynologist (KAU, ACW). Expert, blue cross volunteer, owner of Chinese crested kennel "Salvador Dali" and breedless friend called Fenya. "I can't imagine my life without dogs and I totally support the idea #AdoptDontShop".