I’ve got a confession to make: for a long time I was completely clueless on how to take care of my fish. In my defense, fish are basically aliens; they don’t have fur, they don’t need treats, and they don’t really need affection. Heck, they don’t even breath air like normal, sane-person pets. How can we even relate to these weird, scaly critters, let alone take care of them?

Look at this smug guy. Who does he think he is, breathing water? (Photo: Huy Phan)

It turns out fish aren’t that different from other pets. Ok, admittedly you won’t be taking Mr. Bubbles for a neighborhood stroll anytime soon, but fish still need basic things like a clean environment, good quality food, and a sense of safety and security. You may not believe any of this. You might be saying, “Hey guy, I’ve seen a lot of Disney cartoons, and I know for a fact that happy fish live in bowls. And I’ve seen all the bettas in cups at pet stores! Surely Disney and Petco wouldn’t lie to me, right?”

I’m here to tell you that yes, everyone is lying to you about your fish. I’ve learned many of these lessons over 8 years of experience, both as a professional and as a hobbyist. Luckily, fish owners (yes, you!) are smart, kind, good-looking people, so together we can figure out the truth behind these myths.

1) Your fish can not live in a bowl

Cool picture, terrible home (Photo: Ahmed Zayan)

Unlike us, fish do not have the luxury of flushing away their waste (i.e. poop). When a fish poops it just floats around in the water with them, all the time, until one of two things happens:

The bacteria living in the filter eat the waste and turn it into less toxic chemicals, The fish owner takes out some of the old water and replaces it with clean, de-chlorinated water.

If there is no filter, or if the water is never/rarely changed, this usually means that the fish gets sick because they are literally swimming in their own filthy waste. This is also why fish tanks that don’t have a filter or aren’t regularly cleaned can have a distinctive odor— that’s fish poop you’re smelling.

Fish bowls are so small that the waste builds up very, very quickly, which can lead to the fish getting ammonia poisoning from their own waste. This is not a good way to die, and even if the fish lives for what seems like a long time (in subjective human time), it is probably not living a happy life. So do your watery pal a favor and get him a tank that is properly sized for him.

A good resource for finding out appropriate tank sizes is seriouslyfish.com. They have extensive, research-backed articles on most fish species you can think of.

2) Your brand-new tank isn’t good for fish (yet)

Remember what we said earlier about all that bacteria living in the filter? The ones that eat the poop? These bacteria are part of something called the Nitrogen Cycle, which is a natural process in which bacteria colonizes your aquarium and eats the fish waste, breaking it down into less toxic chemicals. It’s basically the thing that makes having a home aquarium possible. In a nutshell, here’s how it works:

The fish releases waste in the form of toxic ammonia and co2 Nitrosomonas bacteria living in the aquarium (on all the surfaces, but mostly in the filter) oxidize the toxic ammonia, eliminating it. Very toxic nitrite is created as a byproduct. Nitrobacter bacteria converts the nitrites into nitrates.

Both ammonia and nitrite are toxic to fish and can be lethal, while nitrate is not lethal in low to moderate levels. Generally, in order to get rid of nitrates, the aquarist needs to do routine partial water changes.

Why does all of this matter? Those helpful nitrosomonas and nitrobacter bacterias are the only things keeping your aquarium from becoming a gross cesspool, and those bacteria don’t grow numerous enough to do this until approximately a month after you set up your tank.

This means whenever you buy a new tank, you should wait at least month after setting it up to introduce fish. During this time you should also sprinkle a bit of food into the water everyday to give the bacteria some ammonia to feed on. It’s a good idea to get your water tested often during this process — luckily, most fish stores will test your water for free. This also gives you time to get decorations and plan your tank layout. Your nitrogen cycle will be complete when a water test shows 0 ammonia, 0 nitrite, and 0–40 nitrate.

A water chemistry test kit is a an essential tool for aquarists.

A healthy tank will have water chemistry within these ranges.

Fishlore.com has an excellent article that gives more in-depth info on the nitrogen cycle.

3) Fish can, and will, outgrow their tanks

“Don’t worry about that goldfish getting too big, it’ll only grow to the size of the tank” is a common piece of misinformation. If anyone in a pet store tells you this, run away and don’t look back. Fish, especially bigger species like goldfish, need minimum amounts of water volume in order to stay happy and healthy — for just one adult goldfish, this could mean as much as 55 gallons of water. Each fish species has specific water volume needs, so make sure that your tank can accommodate your new friends when they grow to adult size.

When fish don’t get the space they need they become stunted and unhealthy — just like you would if you lived in a closet your whole life and never left.

But don’t despair! Even though bowls aren’t good environments, there are plenty of fish that can live in smaller water volumes. Dwarf pufferfish, endler’s livebearers, and bettas are all good options for tanks 5 gallons and above.

Dwarf pufferfish are vicious, insatiable killers. If you’re a snail, that is. Otherwise, they’re just cute. (Photo: Jonathan_Salant)

4) Fish eat less than you think

So you’re walking by your tank and your favorite fish, Mr. Bubbles, is giving you eyes again. He’s dancing, he’s bubbling, and you’re pretty sure he looks hungry. Come to think of it, it’s been almost 2 hours since you fed him! Surely you can just give him a quick snack, right?

Mr. Bubbles giving you those seductive eyes (Photo: David Clode)

Before you go and give Mr. Bubbles a heaping helping of second breakfast, consider this: that dude can live for at least 2 days before he really starts to notice how hungry he is. In fact, it’s probably best if you fed him only once a day. This varies depending upon the fish species, but for most tropical fish it is a safe rule. Feeding only once per day will keep your fish fit and prevent them from getting sick from overeating. It will also keep the waste levels in your tank down, making maintenance easier on you.

5) Not all fish can live together

Cichlids are the overly aggressive frat boys of the fish world (Photo: Creative Nerds)

A lot of people forget that aquarium fish are never really tamed, they’re just wild fish that we somehow managed to capture in glass boxes. Most of the fish you see in pet stores come from vastly different parts of the globe, and their personalities, diets, and temperaments can be just as varied— if you were to put African Cichlids with Neon Tetras, that would be the equivalent of tossing a lamb into a lion cage.

Much like a RA in a college dorm, it’s your responsibility to make sure that no petty drama escalates into a murder-fest. Although there are MANY different possible combinations, here’s a short list of some compatible species:

Goldfish can of course get along with other goldfish, as well as other coldwater species like Platies, Dojo Loaches, and White Cloud Minnows. Peaceful tropical fish like tetras can live with other peaceful species like corydoras, danios, and dwarf plecostomus. Generally African cichlids should only live with African cichlids due to their territorial aggression.

Panda corydoras, like me, just want to make friends and eat snacks (Photo: The Aquarium Wiki)

For more information on fish compatibility, visit Liveaquaria.com’s compatibility chart.

Want to know more? Here are some more helpful resources: