Top 5 Aggressive Fish Tank Species for Your Home Aquarium

When stocking a new aquarium with multiple pet fish, the two most popular options are community fish and aggressive fish. Experienced aquarists often like to dabble in more challenging species that fall under the "aggressive" umbrella. But what are they, how do you manage them, and which species does this include? We're glad you asked!

What are aggressive fish tank pet fish?

Although their name might put off some potential owners, these fish aren't going to be mean to you! There are two types of aggressive fish. The first group, the bullies, tend to pick on other fish — their own species included — by biting, chewing on fins, harassing, chasing, cornering, and fighting. Some species won't stop until they kill their opponent. The other type of aggressive fish is predatory fish that view tankmates as their next meal.

How to Manage Fish Tank Bullies

As you build a tank of aggressive fish and spend time observing their behaviors, you'll discover which fish are manageable and which are bullies.

You can try rearranging the aquarium decor to mix up the "turf" to confuse the fish and break up any territorial disputes. Also, be sure to spread food evenly over the surface of the water to avoid crowding (and fighting) for meals.

A breeding cage can also be used within a tank to temporarily house an aggressive bully for a few days as a "time out" to help the fish calm down. If the fighting is difficult to manage, you may need to build a single-species-only tank to keep aggression to a minimum or single out the biggest bully to its own aquarium.

5 Types of Aggressive Fish for Your Aquarium

If you're ready to take on the challenge, we've got five of the top species to consider for your aggressive fish tank — feisty and fun but manageable for experienced hobby fish keepers.

1. Exodons

Exodons paradoxus (aka bucktooth tetra) is arguably one of the most aggressive fish you can add to your fish tank. While its appetite tends to be carnivorous, it's a known scale-eater. Meaning few fish in your tank are safe from becoming a snack exodons can nibble on throughout the day.

This silver fish is brightly colored with red- and orange-tipped fins with red, green, and yellow hues along its body. When lighting and water quality are at their best, the fish reflect blue and purple iridescence.

These slow growers are usually found in pet stores around 2 to 3 inches long but can grow up to 6 inches. To keep exodons happy in a group, purchase them at the same time, in a fairly decent quantity (some aquarists say at least 12), and make sure they're about the same size.

2. Oscar

Looking for a big fish to be a solo centerpiece in your home aquarium? Then consider the flashy, sassy oscar! These bright fish can grow to a whopping 18 inches in length. And these jumpers need a sturdy aquarium hood and lots of fun decor to play with, including aquarium gravel to dig in, plants to nudge, and rock arches to navigate in a 55-gallon or larger aquarium home for one fish. Plan for daily interaction with this super-active guy, including treat time!

When oscars are young, they are timid and meek. They become more aggressive as they grow older and larger. So, consider keeping oscars in a separate tank while they're immature. You can house more than one oscar together, but you need a huge (think commercial-grade) aquatic setup for multiple adult fish and risk territorial fighting.

3. Peacock Bass

The peacock bass is a gorgeous fish with colors ranging from greens to golds with three black bars on their backs. Even though they're called "bass," they're actually a member of the cichlid family. Males typically grow a hump on their heads when they're ready to reproduce. Peacock bass are predatory fish that will eat their own species if food is in short supply. Be sure to choose tankmates the same size or larger to keep peace in the aquarium.

Peacock bass are feisty jumpers. They love to dart about the tank, so make sure you get a long tank with a secure lid (to keep them from escaping your aquarium). While the average subspecies grows to around 14 inches long, some will top out at 30 inches. Regardless, you need a large tank (think 150 to 300 gallons) to keep these fish happy and healthy.

4. Midas Cichlid

These brightly colored fish are often mistaken for their cousins, the red devil cichlids. Midas cichlids are large — growing up to 14 inches long. They have a distinctive hump on their heads that appears as they mature, which is larger on males. Midas cichlids are very territorial during mating season, defending a 4-foot territory around their nest. It's a good idea to keep them in a tank no less than 6 feet long and place decor in a way that gives their nest boundaries.

5. Pike Cichlid

Pike cichlids are predatory fish, meaning this fish is a great choice for a single-species tank — and experienced aquarists. They are highly territorial and will kill smaller tankmates and those similar in size. However, these fish have fun personalities and are known to interact with their people and will "beg" for food. Pike cichlids are one of the largest cichlids around (growing up to 15 inches) and will need a large tank (at least 90 gallons). These hardy fish can live up to 10 years, so plan on having them around for a long time.

Keeping an Aggressive Tank Can Be Rewarding

Some fish are simply more lively and entertaining than other species. They may eat smaller fish, stand their ground, chase off predators, and scare others away from their mates — with a vengeance! It's part of their survival instincts to keep themselves and their fish families safe in the wild, and we're lucky enough to see these innate traits in action as pet owners.

Learn more about setting up your aquarium in "Starting A New Aquarium - What to Expect In The First 60 Days."