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I think, therefore I harm

Cats in Fish Tanks

Please note that this article was posted as an April Fool Day hoax. Please, do not drown your cat.

No, I am not talking about catfish. Cats, these feline hairy mammals, can and do adapt to life underwater. This was known by the Ancient Egyptians, and several mentions exist that let us believe it was possibly popular in the late dynasty, once glass was a common commodity. It is possible that keeping cats in fish tanks was also popular in Europe soon after the first contact with the Ancient Egyptians, though the evidences are anecdotal.

A 3-year-old cat "born" in a fish tank

A 3-year-old cat “born” in a fish tank

We all know that cats love fish, despite the fact that fish are poor in nutrients that cats need. In fact, it is recommended to only serve fish to cats as an occasional treat, not as a meal. So why do cats love fish if it isn’t really good for them? As we know, proailurus, the first cats, were arboreal, which means they spent a large part of their life in trees. However, they had large paws which couldn’t have been very good to walk on tree branches. These large paws could have been, in fact, a left over from their direct ancestor, which is believed to be an amphibian mammal, an animal able to live on land and underwater. Polar bear is an extant example of an amphibian mammal, which primarily lives on land (ice, actually), but spends a lot of time in the water. Polar bear has, in fact, very large paws, which is useful to swim, though it is unclear if he inherited these paws from his ancestor or if he evolved them to adapt to his environment.

The attraction of cats to fish may well be a remnant of a period when their ancestor hunted underwater. This would also explain why cats are so light, in contrast to their cousins, dogs and bears. Their short and fine hair would also be explained this way – though many man-made cat breeds were developed with long hair. The fact that cats are able to breath underwater would also be inherited from their ancestor, though their instinct did not keep that knowledge. Obviously, their paws also shrunk in size, adapting better to trees and land. For some reason, most domestic cats fear water, but wild cats did not develop this aversion. It is unknown why domestic cats developed fear of water, but it would most likely be linked to the fact that they originate from the deserts in Africa, where water is scarce.


Aquarium cats love hunting goldfish

Aquarium cats love hunting goldfish

In the modern days, the knowledge of cats being amphibian creatures was rather lost, but was rediscovered recently. In fact, in the last few years, more and more people have begun keeping their cats in aquarium, completely immersed. This makes sense to some, as cats in aquarium don’t scratch the furniture, or spread their hair everywhere. Cats in fish tanks are however not very social, and emphasize their solitary nature further.

A local pet shop recently begun selling cats which are already acclimated to life underwater, as an answer to the growing demand. They claim to be the first one to do so in Canada, but already several pet stores in the USA sell these. I was very surprised to see a cat swimming freely in an aquarium for the first time, but it made sense after I did a little research. It is said that cats living underwater tend to loose a lot of hair at first, because it doesn’t serve a purpose anymore, but the lighter hair wasn’t apparent on those I saw in the tank there. The hair was free floating and the colors were just as livid, if not more, than in out of water cats.

How to

If you don't use a top, your cat may get out

If you don’t use a top, your cat may get out

It is said that the best approach to keeping a cat in a tank is to introduce them to the water right from birth. The cat has his lungs already filled with water from their mother, and therefore start breathing in the water naturally. However, it is apparently very easy to acclimate them to water later in their life, though the younger the cat, the easier it gets. Some people have been successful acclimating their cat to water at an age of five years or more. One must be careful though, as the older the cat gets, the more likely it is that their reflex to breath underwater will not trigger, leading to drowning.

The only technique is to simply push the cat in the tank and hold his head underwater, until he realizes he can breath. The cat will obviously try to rip your hands, so you may want to use gloves. After a while, the cat will relax. If the cat stops moving completely, immediately pull the cat off the tank and begin mouth-to-mouth resuscitation.

If you want to get an aquarium cat, or you decide to try to adapt one of your cats to life in a fish tank, you should know a few things. First, if you are unfamiliar with fish tanks, you should first read my series Your First Aquarium (part 1 and part 2), as most of these also apply to cats.

This tank is too small for this cat. Make sure your cat has a lot of space to play.

This tank is too small for this cat. Make sure your cat has a lot of space to play.

Cats are quite big fish, and need a large tank. For calm adults, a minimum of 125 L / 33 gal. is advised. For more active kitties, you should consider at least 250 L / 66 gal. per cat. You should consider an heavy top, in particular for the first few weeks, to avoid having to run after a wet cat in your house.

Cats cannot live in salt or brackish water. They need very soft water, under 40 ppm, so you may want to use bottled water depending on the quality of your tap water. They do not tolerate chlorine and nitrates at all, so make sure not to use tap water directly and make very frequent water changes. Also, because unlike fish cats have hair, it is advisable to use a larger filter and to clean it very often. Cats prefer warm water, similar to tropical aquariums, in the area of 25-28ºC / 77-82ºF.

Pikachu syndrome is common in cats which have been exposed to chlorine. Eliminate chlorine from your tank and the cat will recover its normal colors within a few weeks.

Pikachu syndrome is common in cats which have been exposed to chlorine. Eliminate chlorine from your tank and the cat will recover its normal colors within a few weeks.

Underwater cats will produce just as much poop as regular house cats, and cats keep their instinct of covering it, so a thick layer of gravel is recommended. Also, since they produce more poops than fish, it is advised to remove most of it at first, to let the bacteria colony adapt to the sudden increase in decomposable matter. Over time though, you will not need to remove it, the bacteria will take care of that. Underwater cats don’t pee as much, but a good activated carbon media is suggested in your filter to take care of the excess ammonia.

Underwater cats can eat regular dry cat food. Obviously, it won’t remain dry, though it floats. Therefore, cats will eat it from the surface. You should remove any remains after about 20 minutes, so it does not pollute the water.

Feeding canned food is out of the question, but you could give them a few living goldfish or a few guppies (from your guppies tank, as they reproduce like rodents and you always have too many) occasionally, as treats. Cats adore hunting fish. I have ran across a lady who claimed treating her cat with butterfly fish, a quite expensive species, because the cat liked the colors. I didn’t bother telling her that cats don’t see yellow.


If you decide to attempt the experiment, please let me know how it went and send me a few pictures. Also, if you already have an aquatic cat, please share in the comments below. I would love to hear about your story, in particular if the fisherman had a good day.

Please note that this article was posted as an April Fool Day hoax. Please, do not drown your cat.


13 comments on “Cats in Fish Tanks

  1. sledpress
    April 1, 2014

    I hope nobody really tries this, but it’s hysterical.

    • Tom Duhamel
      April 1, 2014

      I hope so! After all, it is said that hundred of viewers called the BBC to get details about the annual spaghetti harvest:

      Yes yes, I’ve put my reputation at stakes. But you won’t believe just how much fun I had writing this. I’m glad you liked it as well 🙂

      • sledpress
        April 1, 2014

        Ha! When I was just out of college and doodling with watercolors I painted a cartoon titled “Harvest in Fish Orchard.”

        I should have looked for that and put it up today, I mean, it may still be around here somewhere. Poisson d’Avril!!

  2. heretherebespiders
    April 1, 2014

    I was slightly horrified at the description of how to acclimate your cat, but with such good advice, I think I’ll start setting up a tank next week!

    • Tom Duhamel
      April 1, 2014

      I’ve heard Bengals were particularly good for this 🙂

      • heretherebespiders
        April 1, 2014

        Okay you REALLY have to help me figure out how to upload a video. And you have to know how an iPad isn’t normal 🙂 I have a GREAT one of Spot throwing water all over the floor!

        And I tried to reblog you post and it didn’t work 😦

        • Tom Duhamel
          April 1, 2014

          I used to be the one to contact for any technical stuff. I kind of lost it when they came up with these numerous portable devices. For me, a computer is something that uses an entire desk, top and bottom. I’m definitely not an expert when it comes to these devices. I kind of used them on the occasion, stealing them from relatives or friends to show them stuff (I know my blog looks horrible on a phone). Beside that… I can’t believe you don’t know anyone who knows iPads enough to help you with this.

          YouTube probably has an app or something that would make it easy. Or maybe Vimeo, both work equally on WP.

          As a last resort, catch me on Skype. If I at least know exactly which steps bugs you, I could look it up and see if I can do something.

          (I’d really love to see these cat videos)

  3. Tracesofthesoul
    June 19, 2014

    What an interesting post! I had no idea although I always wondered why some of my cats would whine to come into the bath with me…I am late in reading but I discovered your blog looking for more history on summer solstice la fête de la St Jean. Very informative blog you have!

  4. Tracesofthesoul
    June 19, 2014

    Ha, just read the April fool’s warning!!!

    • Tom Duhamel
      June 19, 2014

      Haha! I can’t believe someone got fooled 😛

      It was written to sound serious and informative, but very little of the information in the post was actually true (for instance, Ancient Egyptians didn’t know glass).

      • Tracesofthesoul
        June 19, 2014

        Well, my kids (adults) do laugh at how naive I can be…this is proof…haha. enjoy your summer and festivities starting, hopefully with fireworks and feu de la St Jean:)

  5. Cool Aquarium
    June 29, 2014

    Cool! haha. At first, I thought the article was really informative I mean, it’s possible. But then I have read the warning at the end. 🙂 You got me there!

    • Tom Duhamel
      July 3, 2014

      The warning was also at the top 🙂 You can tell I like both fish and cats. Yep, it was meant to appear informative, with things inspired by real facts, but all mixed up into fake facts that still sound true. Now you’ll know what to expect from this blog next year lol 🙂

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This entry was posted on April 1, 2014 by in Aquariums, Cats and tagged , , , .
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