Understanding Fish Behavior: A Guide

Fish might look like they’re just gliding around with no real purpose, but there’s a hidden world of fish behavior waiting to surprise you. In fact, the social behavior of fish can be as rich as that of dogs or birds, with some species forming tight schools and even making individual bonds. When you take a closer look, you’ll see different types of fish behavior—from playful chasing to serious guarding—that reveal their real personalities. 

Aquarium owners often note that aquarium fish behaviour isn’t just random darting; it’s full of meaning—colors shift, tails flick, and sounds sometimes ripple through the water to say, “Watch out!” or “Look at me.” This shows the amazing intelligence of fish, like archerfish that can remember faces and cichlids that pick pals based on past good times. Watching their fish communication—the way they move and make noises—helps us understand their needs and keeps them happy and healthy. 

Finally, when you set up your tank with real caves, plants, and open swim zones, you’re encouraging natural fish actions and stronger fish bonding. By learning these clues, you’ll turn your aquarium into a lively, peaceful world where your fish can show off their secret social lives.

In this article, let’s dive in and explore the fascinating world of aquarium fish behavior.

Intelligence of Fish: There or not there? 

Image source: Miguel Del Angel Villegas/Pexels

Contrary to the popular and long-standing belief of fish-noobs, fish aren’t just instinct-driven creatures. Some species display impressive fish intelligence, including fish communication, recognition, and yes, memory. Suddenly, Finding Nemo is a real thing! 

Scientists at Scientific American found that certain fish, like archerfish, can recognize human faces, proving their ability to distinguish individuals. Apparently, many shoaling fish, like guppies and tetras, can identify and remember fellow group members for up to 30 days.

Diving deeper, we came across a Science Daily report that stated that cichlids choose to associate with fish they’ve had positive encounters with before. This suggests memory-based social preference.

These behaviors highlight the evolving understanding of fish friendships, fish communication, and what may be considered emotional intelligence in the aquatic world.

Shoaling vs. Solitary Fish: Types of Fish Behavior

Shoaling Fish: Some fish species thrive in groups, forming schools or shoals to feel safe and secure. Guppies, tetras, angelfish, and danios are naturally social and are top choices for aquariums. These species exhibit group behavior, often choosing preferred companions.

In fact, they engage in an obvious social behavior of fish. Living in a group helps reduce stress and mimics their wild environments.

Solitary Fish: However, one can’t just group any kind of fish together. Not all fish are social. Some are territorial and prefer being alone. The Bettas or Fighter Fish are classic solitary fish. The males are known for their aggression toward others. We can possibly keep at least 5 females together. However, keeping the males in community tanks often leads to stress or fights.

Interested in taking care of fish? Learn more from The Spruce Pets about how to best take care of freshwater fish. 

Unexpected Underwater Fish Bonding

Some aquatic duos go beyond shoaling and form unique partnerships that benefit both parties.

Image source: William Warby/Pexels

The Goby and Shrimp Relationship

One of the best examples of fish teamwork is the goby and shrimp relationship:

To begin with, the shrimp digs and maintains a burrow and the goby fish stands guard at the entrance and warns of predators with tail flicks. It’s a give-and-take behaviour. This partnership shows complex cooperative fish behavior, as noted by Scuba.

Cleaner Fish Friendships

You might have noticed this relationship without conscious effort. The cleaner wrasses and other cleaner fish offer parasite-removal services to larger fish, These guys actually build ‘client relationships’ with repeat visitors. They even famously offer gentle “fin massages” to improve trust and loyalty.

How Fish Communicate: Body Language and Sounds

Fish don’t speak, but they sure know how to send messages. Their fish body language and acoustic signals are key to their social interactions. See if you can pinpoint some in your tank! 

• Color Shifts: Rapid pigment changes can signal fear, aggression, or courtship.
• Tail and Fin Movements: Darting or flicking often warns of danger; slow fins may indicate relaxation.
• Acoustic Signals: Some species use low-frequency clicks or grunts to coordinate with shoal mates 

Observing these cues helps you identify compatibility issues or environmental stressors in real time.

What This Means for Your Aquarium

If you love having fish and aquariums at home, understanding the social behavior of fish will help you create a more comfortable, natural habitat. Let’s list a few dos and don’ts for keeping fish. 

• Keep shoaling fish in groups of at least 5–6 to reduce anxiety.
• Provide hiding spots and tank decorations to simulate natural environments.
• Avoid mixing incompatible species, especially solitary or aggressive types.

Observe interactions — happy fish display smoother, more confident movements.

Image source: Chait Goli/Pexels

Thammaiah Ayappa, a longtime fish enthusiast and aquarium shop owner, shares some important advice for first-time fish parents:

"Before you bring home those bright, beautiful fish, take time to really understand how aquariums work—especially the nitrogen cycle," he says. "It’s the key to keeping your fish healthy, and there are tons of great videos online to help first-timers get started right."

He also emphasizes that getting the setup right from the start makes all the difference.

"Once you've got the basics down—like choosing compatible species, setting up the right tank size, and not overfeeding—you can start picking fish based on their personality," he adds. "Whether you want peaceful swimmers, active shoalers, or bold solo types, there's a fish out there for every kind of fish parent."

So, Finally! Do Fish Have Friends?

While fish don’t form friendships exactly like mammals, they display clear social behavior of fish—forming preferred associations, cooperating in shared tasks, and communicating needs and moods. By embracing their diverse types of fish behavior and fulfilling environmental requirements, you’ll witness richer, more dynamic interactions and foster genuine fish bonding in your aquarium.