The Siamese fighting fish, Betta splendens, warrants its own entry for the sheer number of misconceptions that surround its care.  Bettas (almost always males) are usually sold in small glass bowls with a little gravel or a plastic plant.  They are constantly marketed as the fish equivalent of a houseplant or decorative vase, with dozens of increasingly bizarre tank shapes that all have in common the impossibility of proper maintenance and extremely small size.  The probably discontinued “iPond,” a tiny vessel that vibrates in time with the music playing from a connected iPod to “entertain” the betta imprisoned within, is only the most egregious of these crimes against animal welfare.

It should go without saying, but it often doesn’t: bettas are fish.  They’re not houseplants, or tchotchkes, or quirky accent pieces that really set off the modern art on the other side of the room.  They are pet animals with specific needs and they need to be treated accordingly.

First and foremost: NO FISHBOWLS!  While bettas are obligate air-breathing fish from relatively dirty water, they can’t tolerate the rapid accumulation of their wastes in tiny bowls for as long as people imagine they can.  This is even more so for the fancy varieties that have been bred for their colors over virtually every other aspect of their biology.  They need actual tanks like any other fish, even if their labyrinth organs and relative inactivity mean they don’t take up a lot of tank space.  They also need filtration, but their finnage means they are weak swimmers that can’t tolerate high flow rates.

Also, they’re called fighting fish for a reason.  One thing those tiny bowls do right is that they keep people from trying to house two or more of them together long-term.  Bettas have been bred for centuries to emphasize their violent, territorial tendencies, and males have long been used as an easily-contained alternative to cockfighting in their native lands.  As much fun as it can be to watch a betta flare its opercula and circle a rival, this is a stressful and dangerous experience for both of them, and it’s not unusual for the loser to be beaten to death if no one intervenes.  Pitting a betta against its reflection is less likely to result in a dead fish, but is still a stressful experience.  Bettas’ mindless violence is such that it’s unwise to keep two of them together in a tank of virtually any size, but above 75 gallons the loser can usually get far enough from the winner to not get killed immediately.  Females are less dangerous to one another but are still territorial.  Related fish, such as gouramis, may also activate the betta’s territorial instincts.  Finding out whether the betta’s aggression might best the gourami’s not having had the function of its fins bred out of it is not a winning proposition.

Bottom line: if you fancy a betta, get a regular tank for it, set up a gentle filter, and don’t keep anything else in that tank without careful consideration.  If you succeed, in addition to a long-lived and beautiful pet, you might be able to witness the betta’s truly remarkable breeding behavior.

Here’s another common scenario.  You’ve started small, which is a good impulse if you’re not sure what you’re doing.  But you’re thinking big, and you can’t decide what to put in your 10-gallon foray into fishkeeping.  So you get a little bit of everything: two neon tetras, a Corydoras, a platy, and dwarf gourami.  These five beautiful fish are sure to make a harmonious picture of beauty and interesting behavior for you and yours.  The modest stocking density is a good idea as well.

But those two neon tetras simply hang listless and blanched near the back of the tank, and the Corydoras seems subdued as well.  They’re not going to last very long, and they’re going to be nervous and skittish the entire time they do, because neon tetras and Corydoras are schooling fish that need their own company to be comfortable.  In the wild, these species (and to a lesser extent the platy as well) live in shoals of dozens to thousands and synchronize their behavior as much as possible.  Being alone is a dangerous state for a tiny fish in a river that’s also home to arowanas and matamatas, and schooling fish experience nigh-continuous terror when separated from the collected body of their fellows.  Species like this are at their best in groups of six, eight, or even larger numbers.  That lets one watch a teeming swarm of neon tetras flash their blue markings in unison as they travel around a tank together, or a group of Corydoras all rush to the surface for air at once and rush back to the bottom just as quickly, instead of cowering in the most sheltered place they can find as they wait for the shoal of their fellows that will never come.

Or, in another too-common aquarium nightmare, one gets a pair of strikingly-colored tiger barbs to accent their tank, and watches the little monsters terrorize everything else they can find until all of their tankmates are hiding in corners with ripped fins and missing scales.  The mistake, in this case, wasn’t in the choice of tankmates, necessarily, but in getting only two tiger barbs.  This species, like many others, establishes a pecking order and enforces it with near-constant small acts of aggression.  In a group of at least eight, they confine this attention to their own kind, which can tolerate this treatment, and leave other species alone.  In a smaller group, though, they dump all of that energy on whatever other fish are handy, with disastrous results.

The lesson here is, it’s important to know whether the latest addition you’re contemplating for your work of aquatic art needs to be part of a bigger scene, or is safe to include by itself.  Your fishy friends will thank you.

Conversely, some fish can’t stand their own company.  We’ve already met the betta, which was bred to enhance the natural territorial instincts of anabantoid fishes to gladiatorial levels, but there are other, less intense examples.  Many species establish territories and defend them aggressively.  Some species, like most gouramis, are content to police their homes against related or similar-looking species only, and become an issue only if one tries to house more than one in a small tank.  Others, though…

This horror story comes from my own experience.  I had a tank in Miami with a small group of black neon tetras, a few catfish, and two blind cavefish.  I wasn’t doing everything quite right, but my single biggest mistake was adding two African mbuna cichlids from the Flagler Flea Market to the mix.  Those two little monsters proceeded to eat everything in the tank small enough to fit into their mouths and to bore into the undersides of the cavefish.  Soon, it was just them, one zebrafish too big to eat and too small to be a threat, and some of the catfish, until I could separate them.  Of course, the tank wasn’t even big enough for the two of them by the time they were done growing, and the smaller one hid behind the filter intake while the larger claimed the entire tank.  In my bucket while I set up a new tank and their separate housing, the smaller one mutilated the larger’s tail, and the larger one didn’t last much longer.  The remaining beast lasted for years, and proved to be a charming pet once I housed it only with animals that made trouble in my main tank, such as a crayfish that killed a lot of my plants.

I made several mistakes in acquiring those cichlids.  I thought I was getting one of the benign species, but I misidentified the vendor’s offering and got one of the more aggressive varieties instead.  I put them in a tank that was barely large enough to be one of their territories, let alone two, and they acted accordingly.  But once I had them separated, I could treat them properly…or the one that killed the other one, anyway.

African cichlids are only the most famous of these tank-killers.  Territoriality is another variable one has to consider when picking out their fish.  Some fish school—and some fish home-school.

This is, as far as I’m concerned, the most tragic of the aquarium trade’s assorted misconceptions.  Lots of us have this idea that some fish are “cleaner fish,” whose role is to “clean” the tank.  People imagine that these fish—usually catfish, loaches, and other bottom-feeders—eat other fish’s feces, or otherwise subsist entirely on this “cleaning” chore.  People likewise imagine that “cleaner” fish are the solution to tanks that have not been maintained, and will replace water changes or new filter media.

All of that is wrong.  The fish people think of as “cleaner” fish actually subsist on leftover food from the upper levels, not the feces or other leavings of their tankmates.  In a tank whose other fish are being “overfed,” the bottom-feeders might find enough to thrive.  But most of the time, this perception that bottom-feeders subsist on fish feces and goodwill puts these fascinating animals on a slow path to starvation.  Worse, many of the most popular bottom-feeders are South American armored catfish, whose bodies are encased in bone and can’t thin out or cave in if they’re underfed.  Right until the moment they starve to death, they look perfectly happy (or quiet and bored, if they’re Corydoras and are being kept alone).  Many, such as loaches, are also sensitive about deteriorating water conditions, and among the first victims of New Tank or Zombie Tank Syndrome.

Algae eaters often have it worse.  Many of them refuse to eat certain kinds of algae, leading to unpleasant situations where the addition of the algae eater does nothing to affect the algae levels in the tank, with the fish slowly starving or seeking other food sources.  This is particularly true for very dirty tanks that have started growing cyanobacterial slime, which few fish will touch.

Or you made the mistake of buying a Chinese algae eater, which quickly learns that flakes are a more efficient food source than scraping bits of green off of rocks, grows larger than people realize, and starts eating holes in other fish’s skin as it gets older.

All of your fish are your pets.  None of them are appliances that service the rest of your system.  If you get bottom feeders, buy them sinking food and, for fuck’s sake, don’t call them “cleaner fish.”

There are still a few specific and unusually frustrating situations an aquarist can get into if they don’t bring appropriate skepticism to the store with them.  I address the most common of those in the third and last installment.  Would you believe this all fit in a 12-minute presentation?