Aquatics Unlimited: Articles: Terrible Two's
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THE COMMUNITY AQUARIUM: PRINCIPLE NUMBER 5

"Terrible Two's"

Perhaps the old adage is correct: two (humans) can live as cheaply as one - provided they share clothing, eat on alternate days, and don't get a joint checking account. But in the fish world, keeping two fish of the same species together often results in the added expense of disposing of one of them. While some varieties of fish, most notably some of the South American cichlids, tend to hang out in pairs, most other varieties do not. Some of these, like most of the danios, barbs and tetras, hang out in schools. In other families, including many gouramis and "mbuna"-type African cichlids, each male stakes out a territory and tolerates a female in the vicinity only long enough to spawn.

A classic recipe for trouble involves the kissing gourami, Helostoma temmincki. These are often purchased in "pairs," which is loosely defined as "the first two fish the fish-store clerk manages to get into a plastic bag." This sounds like a cute idea, especially in light of their fascinating "kissing" behavior, in which two fish approach each other, lips fully extended, and appear to smooch away with the dramatic passion of a Rudolf Valentino movie.

The jury is still out as to whether this activity is evidence of romance or merely a strange extension of their grazing/feeding behavior (Next on Sally... "Is It Love? - or Just Skum-Sucking?"), but one thing's for certain: neither fish is looking for a long- term relationship. Even the few kissers that exhibit the actual "kissing" behavior spend much of their time chasing one another, and before long one of the two gets the upper hand.

From that moment on, the two fish embark on divergent paths: the slightly stronger fish grows bigger, healthier and more aggressive, while the underdog becomes a weaker, sickly, timid runt. As such, a tiny advantage in size or assertiveness leads to an ever-widening gap. And as the difference in their status broadens, the stronger fish tolerates the weaker less and less, until he drives it to an untimely end.

Avoiding this situation isn't very difficult; all we have to do is keep some number of kissers other than two. (A mathematician friend of mine assures me there are plenty of numbers left.) A solo kissing gourami is ok; a quartet generally works as well; and even a trio usually lives in harmony (hehehe...). It's only the duet that routinely seems to strike a sour chord. And that makes a certain amount of sense. If the most aggressive or toughest fish has two, three or ten others to chase around, it's not likely any one will be harassed to the point of physical or emotional injury. However, if there's only a single fish that gets all the negative attention, it's inevitable that it will lose ground - and probably fins and scales as well.

PhotoSometimes close is good enough. Fish don't get quite as hung up on their taxonomy - ormbuna even appearances - as we humans do. A group of eight of the various blue/opaline/gold/platinum/lavender gourami varieties (man-made color morphs of Trichogaster trichopterus) often peacefully co-exists even if there are only two of each type. Similarly, in a large colony of African cichlids most fish are two busy defending their territory from everybody else to worry about how close the next guy is on the family tree.

Sometimes it's not. The small groups scheme works best if all the fish of a given type are as identical as possible. For example, if we attempt to keep four small redtail sharks (Labeo bicolor) together with one huge one, the big guy might well be powerful enough to keep all the others cowering. Or if we buy two adult Boesmani rainbows (Melanotaenia boesmani) to go with our dozen juveniles, it's quite likely the two will totally ignore the younger twelve and go about the business of attempting to intimidate or annihilate one another. Even sex is a factor (isn't it always?) - two male opaline gouramis (Trichogaster trichopterus) or red velvet swordtails (Xiphophorus helleri) will likely duke it out unless there are an abundance of females present.

Many groups of fish exhibit this anti-duo behavior; so many, in fact, that a good rule of thumb is to NEVER buy fish in pairs (with the possible exception of a "pair" of females). The following are especially risky:

  • Redtail/rainbow type sharks (Labeo sp.)
  • Chinese algae eaters (Gyrinocheilus aymonieri)
  • "mbuna" African cichlids (Pseudotropheus, Melanochromis, Labeotropheus, sp. etc.)
  • immature American cichlids including angelfish (Cichlasoma sp., Pterophyllum scalare)
  • Rainbow fish (Melanotaenia sp.)
  • "Fancy" plecostomus (Ancistrus and Peckoltia sp.)
  • Gouramis (Trichogaster, Helostoma and Colisa sp.)
  • male Mollies (Poecilia sp.)
  • male Swordtails (Xiphophorus helleri)

This article originally appeared in
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Freshwater and Marine Aquarium Magazine

Copyright © 1997 James M. Kostich
All rights reserved.

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