Cats are fascinating creatures that often mix having a playful side with deeply ingrained instincts. It’s this combination that can mean they love sitting in front of a fish tank, mesmerized by what they’re watching.
Sometimes they may paw at the glass but mostly it seems like an innocent fascination. But what is it about fish that causes this reaction? Here we’ll explain all of their secrets.
Instinctual Hunting Drive

Cats are natural predators, and their potential prey is seemingly only limited by what they can kill. You may not think fish would be a natural target of cats, but this isn’t true. Cats can have excellent fishing skills, especially in shallow water.
The movement of the fish swimming through water will trigger their natural prey drive. This is the same reason they enjoy looking at birds through a window. Even if there is a physical barrier to their prey, they can enjoy tracking them.
When hunting, cats can be incredibly patient, which most likely explains why they can stay calm while watching the fish. They instinctively know to stay still when required and track their prey until the right time to pounce. Hopefully with a fish tank, that never actually happens!
Visual Stimulation

Cats have incredible eyes that are perfectly suited for their environment. Their short and long term focus isn’t great, and they don’t see the same range of colors we do. However, they are incredible at seeing in the dark but also detecting movement.
Where a rapid moving fish may be a blur to us, it can be a clear image to a cat. This gives them a visually stimulating experience. You may have found this with cat toys, but cats are instantly curious about anything that moves around.
The unpredictability of fish movement will keep their minds engaged for long periods of time. It’s almost like a source of TV for cats and helps to prevent them from getting bored.
The Soothing Effect of Water

For many humans, seeing a body of water can bring a sense of calmness. It could be as vast as an ocean or as small as a fish tank. It’s part of the reason why having fish can be great for your mental health.
It can be similar for cats. They may find the movement of water calming. The gentle bubbling of the filter, fish of all colors darting around, light reflecting through the water. All of this can be a nice stress-relieving activity.
This may be partly instinctive too. Moving water in the wild often means fresh water from the likes of streams and rivers. Some cats are drawn to running water, which may be because they see it as naturally safter than stagnant water.
Curiosity About the Unknown

Of course, cats are notoriously curious creatures. They love to search for anything new and explore their environment. A fish tank is no exception, especially as with the likes of plants and decorations that can add to the mystery.
Cats need to have enrichment in their lives. Fish owners may feel the need to hide their fish from the cat but as long as your feline friend can’t get to them, it can help to reduce stress and prevent boredom.
Can Watching Fish Frustrate Cats?

Yes, and it can be a fine line knowing if it’s good or bad for them. Cats can experience frustration when looking at any potential prey they can’t reach. This could be looking at birds and squirrels though a window, or fish in an aquarium.
Some cats seem content with not being able to catch this prey, whereas others will be irritated. It also appears that some cats will initially be frustrated but learn to accept it over time and come to see it as a form of entertainment.
There are a few signs of them being grumpy in these situations. Chirping, tail twitching, pawing, and scratching are all warning signs. This can lead to redirected aggression, such as your cat biting you if you try to move it away from the glass.
It’s a good idea to simply observe your cat and look for these signs. Occasional glass-watching can be good for them, but it should also be mixed with other enrichment activities, such as toys and puzzles.
Potential Risks of Cats Watching Fish Tanks

Most of the time, watching a fish tank will be harmless fun for a cat. At other times, it can cause issues. Firstly, you want to ensure your tank is secure enough that it can’t be knocked over, as cats will try to climb or push against the aquarium.
You’ll also want to look for any signs of stress with your fish. This can happen if your cat is getting obsessively close to the tank and pawing at it. Pawing and scratching can cause other issues, such as damage to the tank and its seals.
Of course, they may also dip their paws in the water. Aside from the obvious risk of the cat clawing at the fish, this can also add contaminants into the water. It can also lead to huge mess or injury if they fall in.
How to Safely Allow Your Cat to Watch a Fish Tank

The most obvious starting point here is to make sure the cat can’t get to the fish. If you can’t provide a lid for your aquarium, then it’s best to keep the cat away from the room the aquarium is placed in.
The tank needs to be secure and incapable of being knocked over. This won’t be an issue for large tanks, but smaller ones need a sturdy stand or surface. Cats know how to use their body weight, and you should bear this in mind.
You should also provide your cat with other forms of entertainment. If the fish tank is their only source of entertainment, they can become fixated on the fish. As always with our pets, it’s important to observe them and take appropriate action when you see a change in behavior.