Do fish get bored? Yes and no. It is difficult to transfer our understanding of boredom into the world of fish. But fish need the stimuli of their natural environment to thrive. If their needs aren’t met mental health problems can occur. The concept of boredom is what fits this situation most.
If you are an aquarium owner you don’t have to despair at this point. It’s not cruel to keep fish in a tank in general. But be aware of what good care means for the species you choose.
Keeping a goldfish in a bowl isn’t a good idea at all!
What The Science Says About Bored Fish
Obviously fish can’t talk to us, nor can we read their emotions through mimics. So it can be hard to believe that fish can feel pain and joy. But they can. 
That being said, fish are highly intelligent creatures with memory and the ability to learn. Some species can even learn faster than dogs. 
Squids and other cephalopods like octopuses for example are known to solve riddles and very basic mathematics.
These smart species need a lot of mental enrichment to thrive. If it is missing they degenerate into sad beings that won’t live very long.
What fish need depends on the species and can vary widely.
Schooling fish like tetras need social interaction with conspecifics to be happy. Betta fish on the other hand are aggressive and territorial so they better stay on their own.
You should learn a lot about the species of fish before you decide to buy it. That way you can care for your pets in a way they deserve.
If the needs aren’t met the result can be abnormal behavior which is often referred to as boredom.
How To Tell If Your Fish Is Bored?
You will get to know your aquarium fish over time and gain experience in telling whether they are happy or not.
Some signs are a clear indicator of stressed and bored fish. Of course, you should always have the natural behavior of your species in mind.
What’s strange for one species might be normal for the other one.
Most of the things I mention below can also be the indicator of illness. Have that in mind and observe your fish closely before you start with the wrong treatment.
So let’s dive into the indicators of boredom in fish.
Lack of activity
Most fish like to be active. In nature, saltwater fish have the whole blue sea to explore while freshwater fish like to play in the currents of rivers.
They explore new things in their ever-changing environment. Hide in underwater grass and dig in the sediments.
In a fish tank, these activities are limited but if you keep it right they should swim and interact with each other.
If your fish is standing still in one corner of the tank or hiding behind some plants that might the sign of a bored and stressed individual.
Of course, there are species like the betta fish that are generally more passive. Take that into account.
Abnormal behavior is a clear sign that there is something wrong.
If a fish that normally enjoys staying on the ground is leaving its area and staying at the top under the water surface and vice versa, often stress is the cause.
This is also for schooling fish that stays on its own without interacting with his school. Or is he even aggressive? You should definitely change the situation.
Some fish tend to self-destructive behavior when bored or stressed.
In the case of siamese fighting fish, this refers to tail baiting where the fish bites his own tail. That doesn’t sound serious but you have to act quickly.
Especially betta fish with their beautiful tails can bite it in half within a few hours. Something you want to avoid under all circumstances.
Glass surfing is when your fish swims up and down the aquarium glass.
Stress is the main reason for this behavior. Often you can watch fish that you just released into the tank glass surfing.
In this case, the cause can be stress from the transportation but you should observe if this abnormal act remains.
A variety of courses such as overstock, unsuitable tank mates or an unsettled environment of the tank can be considered.
How To Prevent Boredom In Fish?
There is a lot you can do if your fish are bored.
Be prepared to try a few things and observe your pet fish. Sometimes the cause of boredom isn’t clear at the beginning.
If you made big mistakes while setting up your tank you might have to do it all again. But your fish will thank you.
Have in mind, that some type of fish like sea dragons should never be kept in tanks.
Reasonably sized tank
A goldfish in a bowl is the best and at the same time most terrifying example for an aquarium that is too small.
To be honest it can’t even be considered being an aquarium.
Even fish that are often kept in a small vessel like betta fish need at least a 5-gallon tank.
According to PETA, you should provide at least 24 square inches of water per inch of fish. 
Bigger is always better and you can’t go too small if you have space in your house or flat.
In large tank poor water quality is also more unlikely.
Tanks with life plants definitely look better. Additionally, they will provide hiding places for your fish.
When you plant your tank take notice of its different parts.
Place small plants into the foreground and larger ones into the background. Look into that you have low and high plants in your aquarium.
Stones and wood
Stones and wood are super tools to structure the tank.
They serve as hiding places and can mark territories.
Some catfish also need to feed occasionally on wood for healthy digestion.
Together with big plant leaves, stones and wood are often used for spawning by several fish.
Every tank should have sand in it.
Some fish like to dig and forage on the ground. Without a soft and compartmentalized ground layer, these species will get stressed soon.
Some fish simply can’t get along with each other and some need a whole group of their own species to be happy.
Plan your stock accordingly and make sure every inhabitant’s needs are met.
After overstocking and small tanks, the wrong mates are the most common reason for stress in fish.
Inform yourself about the different species and their habits. Staff at the pet store don’t know which species you already keep.
Often beginners come home with new fish that are inadequate mates for the ones they already have.
Imagine you would have to eat the same food day in day out. I bet your life would suffer quality fast.
It’s the same for your fish. Especially dry flakes can get boring soon. But they are also considered balanced.
I recommend adding some variety and feeding frozen food every second day. Bloodworms, larvae or brine shrimp are great and provide a lot of enrichment.
As a responsible pet owner, you should add something new to the diet from time to time.
Wrapping Things Up
Fish can be bored and show abnormal behavior when the right stimuli are missing. Usually, this leads to stress which is the biggest reason for fish dying in captivity.
If you are concerned about the mental state of your pet fish, observe them closely. If you determine something unusual you should act.
Be careful to not conflate illness with boredom.
There is a lot you can do to enrich the lives of your fish like rearranging plants, stones and wood or changing the diet.