How to keep cat out of your fish tank

If you have a cat and a fish tank, you already know the struggle. Cats don’t see aquariums as decoration — they see them as a moving screen, a water source, and something they absolutely need to investigate. And if your tank is open, it’s only a matter of time before a paw goes in, a lid slides, or something gets knocked loose.

Most of the time it’s not aggression, it’s curiosity. Fish move constantly, water reflects light, and the top of a tank is warm and elevated, which cats love. Add the fact that many cats prefer “forbidden” water over their own bowl, and an uncovered aquarium becomes a magnet.

People usually try deterrents first. Foil, double-sided tape, sprays, motion sensors. Sometimes they work… until they don’t. The problem is that deterrents rely on your cat choosing to behave. A physical barrier doesn’t.

The most reliable way to keep a cat out of a fish tank is a properly fitted lid that actually stays in place. Not the thin plastic covers that bow, and not glass canopies that weren’t designed to support weight. Cats will jump on tanks, sit on them, and occasionally launch themselves off them. If a lid can’t handle that, it’s not doing its job.

Another issue with flimsy lids is gaps. Even small openings around filters or cords are enough for a curious paw. Once a cat realizes there’s access, they’ll keep trying. A snug-fitting lid removes that temptation entirely and also helps with evaporation, jumping fish, and general tank safety.

There are a few extra things you can do to make your tank less interesting to your cat. Keep fresh water available elsewhere, especially if your cat likes running water. Avoid placing tanks next to furniture that makes them easy to jump onto. Reducing glare and reflections can also help since flashing movement catches a cat’s eye.

But at the end of the day, the lid is what solves the problem long term. Many aquarium owners end up going with custom lids because they’re designed to fit the tank exactly and handle real-world use — including cats. If you’re looking for something strong enough to keep your cat out of the aquarium without looking bulky or homemade, you can order custom aquarium lids from walterlids.com that are built to sit securely and hold up over time.

Keeping your cat out of your fish tank isn’t about constantly correcting behavior or stressing either pet. It’s about setting the tank up once, the right way, so everyone stays safe. With a solid lid in place, you can stop worrying about paws in the water and just enjoy your aquarium the way it’s meant to be enjoyed.