Experienced aquarium owners know they should research different fish species before putting them in their tanks. Some fish are very aggressive and will fight with or eat their tank mates. Meanwhile, certain species are territorial and will even skirmish with their own kind. This is something for every newcomer to be wary of because fish are an expensive investment, and the results can be traumatic. Let’s look at some of the most aggressive pet fish species now.
1. Betta Fish Are Notoriously Aggressive
There’s a good reason why betta fish are also known as Siamese fighting fish. They are a notoriously aggressive species with a penchant for male-on-male violence. Never keep two males together because they will clash. However, keeping a pair of females may be safer because they’re more docile.
Most owners agree that they’re usually poor tankmates with other species. It’s better to put them with less brightly colored or bigger species. We recommend a 20-gallon community tank with plenty of plants and hiding places if you mix bettas with other fish. They’re beautiful, but they have a justifiable reputation.
2. Clown Triggerfish Are Known to Attack People
Clown triggerfish are another spectacular but aggressive species and will even attack humans. There are reports of them attacking scuba divers in the wild. This territorial fish also becomes more vicious and contrary as it grows older. Never house them with invertebrates or smaller species because they will prey on them.
They’re not social animals so don’t worry about keeping them alone. However, you can mix them with groupers, angelfish, and certain moray eels. Owners should note that clown triggerfish have a nasty bite so be wary when feeding them. They’re particularly aggressive when defending their nests or during breeding seasons.
3. Arc-eye Hawkfish Can Stress Their Tankmates
There are several varieties of hawkfish, and most of them have aggressive personalities. However, the arc-eye hawkfish is perhaps the most notorious. This territorial species will make life miserable for new additions to the tank. Owners should be wary because stressed fish are more susceptible to diseases. This species will even attack larger fish because they have no fear.
Most experts advise a 55-gallon tank with many hiding places and plants if you’re keeping Arc-eye hawkfish. They grow to about eight inches in length. Certain blennies and gobies will live harmoniously with them if you want a mixed tank. Don’t put them with crustaceans because they will eat them.
4. Maroon Clownfish: Not So Funny
Most clownfish species are very sociable and docile. However, the maroon clownfish is a very aggressive exception. This eye-catching little fish is very territorial and will claim the entire tank. Some owners even report them jumping out of the water when they open the tank lid! Never mix maroon clownfish with other clownfish varieties because it won’t end well.
Beginners should avoid these fish because of their violent tendencies. If you keep a community tank, we advise adding the maroon clownfish last. Blennies and dwarf angels are some of the best tankmates for them.
5. Wolf Cichlids Have a Strong Bite
Cichlids are one of the most predatory pet fish species. Arguably, the wolf cichlid is the most aggressive sub-variety. These mean fish even pose a threat to their owners. Some home aquarium keepers wear a chain glove because the wolf cichlid has a vicious bite. They can grow up to 30 inches long so they’re not suitable for most home tanks. We recommend a minimum tank size of 125 gallons for this large fish.
Wolf cichlids also possess remarkable intelligence and require stimulation. It’s perfectly fine to keep one alone but you need to provide enrichment for it. Some of them will play with ping-pong balls which can be very entertaining. They also live for up to 30 years so they’re a long-term investment!
6. Lionfish Have Sharp Spines
Lionfish are an extremely predatory and invasive species. They have a very striking appearance with long spines that make them very popular with saltwater tank owners. Remember to take care when handling them because those spines sting and can trigger allergic reactions. Unlike cichlids, their aggression is usually defensive, but it’s still risky.
We advise putting lionfish with larger fish like tangs and larger angelfish because they won’t prey on them. Groupers and rabbitfish are other good options. Experts advise a 120-gallon tank for a fully grown lionfish. Prospective owners should note that they’re a banned species in some jurisdictions, including Florida.
7. Oscar Fish Are Predatory
Oscars are another predatory species. They’re not as aggressive as cichlids, but they’re still territorial and will pick on smaller fish. Oscars will eat anything that they can fit into their mouths. That’s why first-time fish owners should take care when pairing them with other species or introducing them to a community tank.
They will naturally eat smaller whole fish in the wild. Again, it’s crucial to have plenty of hiding spaces in the tank to protect other species. Convict cichlids and Jack Dempsey fish are good tankmates for the Oscars. We recommend a 75-gallon tank for a single adult Oscar. Males will fight each other, and they have a nasty little bite.
8. Jaguar Cichlids May Eat Their Tankmates
This freshwater species is another highly aggressive cichlid. They’re especially temperamental during breeding seasons. They’re not the best option for new home aquarium owners because they will eat their tankmates including smaller species and invertebrates. You’ll also need a larger tank to reduce their aggression because they’ll stick to one territory.
Convict cichlids and various plecos can make decent tankmates for jaguar cichlids. However, there are no guarantees with this aggressive species. They’re not as big as wolf cichlids but maybe even more belligerent. They grow up to 24 inches long and will bite careless owners, so be mindful!
