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Most Aggressive Freshwater Aquarium Fish

When choosing fish for a home aquarium, not just any fish will do! As an aquarist, you must research different species in advance to determine if they’re compatible with other aquatic creatures in a freshwater community tank. Right now, you may be wondering which ones are the most aggressive?

The 20 most aggressive freshwater aquarium fish include silver arowanas, bettas, bichirs, bucktooth tetras, honeycomb plecos, red-bellied piranhas, pea pufferfish, rainbow and red-tailed sharks, tiger barbs, and 10 different species of cichlid fish.

Now that you know which species of freshwater aquarium fish are the most aggressive, let’s explore this topic further. Together we’ll learn more about each species including where they originate, how big they get, what size aquarium is best, and what (if any) fish make suitable tankmates. We’ll also discover if the ever-popular angelfish is considered aggressive.

So, if you’re ready to learn more about predatory freshwater fish and how to care for them in captivity, then let’s get to it!

Which Freshwater Aquarium Fish are the Most Aggressive?

The 20 most aggressive fish you can keep in a freshwater aquarium include the following:

Arowanas (Silver)

Silver arowanas can be found in the blackwater floodplains of the Amazon River. They grow to a massive 3 feet in length and are highly predacious. Therefore, they require a huge tank – at least 250 gallons in volume. They’re best kept alone or with other carnivorous fish of like size and temperament.

Bettas

Betta fish originate in Southeast Asia and are very popular in the aquarist trade. Highly aggressive towards others of their kind, they’re best kept alone or in male-female pairs. Tankmates should be similar in size and disposition. As carnivores, you can also house them with larger, omnivorous fish.

Bichirs

Bichirs are bottom dwellers found in freshwater rivers in Central Africa. They can grow to enormous lengths of over 20 inches and therefore require an extra-large tank – 90-gallons for just one! Being carnivorous, they’re naturally aggressive. Keeping them with fish their size or smaller is discouraged.

Bucktooth Tetras

Bucktooth tetras can be found in the Amazon River basin. They grow to around 4 inches in length and do best with others of their kind since they’re a shoaling fish. Because of their natural tendency towards aggression, this carnivorous fish should be kept in a large species-only tank (60 gallons) in groups of 12.

Convict Cichlids

Convict or zebra cichlids are native to freshwater lakes in Central America. They grow to roughly 5 inches long and are best kept in a large, 100-gallon tank in groups of 6 since they’re a schooling fish. Tankmates for this omnivorous fish should be of equal size and like temperament, including other types of cichlids.

Flowerhorn Cichlid

Flowerhead Cichlids

Flowerhorns originate in Malaysia and are the result of a hybridization between the red devil and the blood parrot cichlid. They reach adult lengths of 12 inches and require an extra-large tank (100 gallons or more). These omnivores are best kept alone or in pairs with other fish of like size and temperament.

Jaguar Cichlids

Jaguar cichlids are a freshwater fish found in ponds and springs in Nicaragua. They can grow to a whopping 24 inches in length and just a single fish requires a large, 75-gallon aquarium minimum. As a carnivore, it’ll prey on smaller tankmates so keep it with other cichlids of like size and temperament.

Jewel Cichlids

Jewel cichlids are found in both freshwater lakes and brackish water lagoons in West Africa. This species reaches full-grown lengths of 10 inches and requires a medium-sized tank (30 gallons) for just one. These omnivores can be housed with other cichlids of like size or peaceful, larger bottom dwelling fish.

Red Devil Cichlids

Red devils are a type of cichlid native to freshwater lakes in Central America. They grow to lengths of 15 inches or more and require at a 55-gallon tank minimum for just a single fish. This species is omnivorous and territorial and best kept alone or with just one or two other cichlids of like size and temperament.

Texas Cichlids

Texas cichlids are native to lakes and rivers in Central America. They reach lengths 12 inches and require a 55-gallon tank for just one fish. This omnivore can be kept with other large Central or South American cichlids, provided there’s enough space in the aquarium for each fish to claim its own territory.

Wolf Cichlids

Wolf cichlids are found primarily in lakes and rivers in Central America. They reach full-grown lengths of up to 30 inches and require an extra-large 150-gallon tank. As a type of carnivore, this species will prey upon smaller tankmates, so they’re best kept alone. They should only be paired when it’s time to breed.

Green Terrors

Green terrors are a type of cichlid fish that originates in South America. They can grow up to 30 inches in length and are best in kept alone or in pairs in a large, 75-gallon tank. This species is omnivorous and can be kept with a few different cichlids of like size and temperament or other, larger bottom-dwelling fish.

Jack Dempsey

Jack Dempsey fish are a type of south American cichlid and found in murky waters near Honduras. Active and aggressive, this species can grow to 8 inches and is best kept alone or in pairs in a large (100 gallon) aquarium. Tankmates for this carnivorous fish should be of equal size or larger, if omnivorous.

Oscars

Oscars are a South American cichlid and found in the Amazon River. Adults reach lengths of 12 inches and need plenty of space in an aquarium to limit their hostile tendencies. A 55-gallon tank minimum is recommended for this omnivorous fish. Keep them with other species of like size and temperament.

Plecos (Honeycomb)

Honeycomb plecos are bottom dwellers native to central Brazil. They can grow to 10 inches long and need lots of space in an aquarium to reduce their natural aggression – an extra-large tank (150-gallons or more) is required. This herbivore should be kept with fish that prefer to dwell in the top half of the tank.

Piranhas (Red Bellied)

Red bellied piranhas are found mainly in South America in the Amazon River. The sheer size and voracity of this species requires an extra-large aquarium (100-gallons or bigger). They’re a type of schooling fish and best kept in a species-only tank. As omnivores, they’ll eat both plant- and meat-based foods.

Pufferfish (Dwarf, Pea, Pygmy)

Dwarf or pea/pygmy pufferfish originate in lakes and rivers in India. Though small (about an inch long), they can be quite hostile in a community environment. This carnivorous fish is best kept alone in a nano (10-15 gallon) tank or in small groups of 5 of 6 in a mid-sized (20 to 30 gallon), species-only tank.

Rainbow Sharks

Rainbow sharks are bottom dwelling fish native to Indochina. They’re highly territorial and can’t be kept with others of their kind. Just one per tank is recommended – a 55-gallon aquarium is perfect for these mid-sized (6-8 inches long) fish. These omnivores can live peacefully with mid-water schooling fish.

Rainbow shark

Red-Tailed Sharks

Red-tailed sharks are found primarily in Thailand. These omnivores grow to lengths of around 6 inches and need a 55-gallon tank minimum for just one. If the aquarium is big enough, you could keep a pair together with other peaceful fish of like size or schooling fish that dwell in the upper half of the tank.

Tiger Barbs

Tiger barbs are native to Borneo and Malaysia. They grow up to 4 inches long and almost 2 inches wide. This species can be quite aggressive and isn’t a good choice for a community tank environment. Instead, keep these omnivorous fish in a mid-sized, a species-only tank in groups of at least 6 or more.

Are Angelfish Aggressive?

Angelfish are semi-aggressive and can become territorial when housed in an overcrowded aquarium. To reduce their hostility, keep them in a large, planted tank with other peaceful fish of like size or at least 2 inches in length. Keep the number of males and females balanced and make sure the fish are well fed.

Final Thoughts

To sum-up, silver arowanas, bettas, bichirs, bucktooth tetras, honeycomb plecos, red-bellied piranhas, pea pufferfish, rainbow and red-tailed sharks, tiger barbs, and 10 different types of cichlids are the most aggressive freshwater aquarium fish. Predatory, carnivorous fish are typically hostile in temperament.

I trust this article has provided you with the information you seek regarding which freshwater aquarium fish are the most aggressive. Thanks for reading and best of luck with your aquarist hobby.

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