"Beware the Little Nippers"
Many common and otherwise popular tropical fish seem to have developed a bad habit - they get their kicks by chasing, nipping and generally harassing their fellow tankmates. What novice aquarist hasn't experienced - or at least been warned of - putting a few tiger barbs into a happy community tank, only to find their prize angelfish and fancy guppies de-finned a few days later?
The likely perpetrators and victims in this situation are a little harder to predict than in Principle 1 - we can't just look at comparative size and guess whether they'll be buddy-buddy or bitey-bitey. Instead, we need to look at their personalities.
The aforementioned tiger barbs are the classic example. In nature, these black-striped beauties are found in schools - not for educational purposes, mind you: they're just there to hang out with their buddies. The only problem is, their entire socialization experience seems to revolve around chasing, fin-nipping, and just plain rudeness. Perhaps there is some deeply evolved value to this behavior, such as some need to maintain the purity of the single-species school; or maybe these fish are just being playful; or maybe they're engaging in the ichthyo-social equivalent of teenage boys elbowing each other in the hallway.
But regardless of the motivation, this activity seems to do no harm to the barbs themselves. They just go on merrily taking - and receiving - these little pot shots. Unfortunately, this is not the case for other fish that are not accustomed to this sort of behavior. Putting a couple of small angelfish or fancy guppies in with a handful of tiger barbs in a small tank is like asking 3rd grade ballerinas to play in the NFL.
I suppose we could blame the barbs for their socially unacceptable behavior - but hey, they're just doing what they've always done, what they're programmed to do. And so are the angels and guppies - it's just that the two groups shouldn't be trying to do their thing in the same place at the same time.
Many of the schooling barbs, tetras and danios exhibit a tendency to nip at least occasionally, but few fish are as predictably nippy as tiger barbs. Fin-nipping seems to be much less of a problem if fish are kept in bigger groups; even tiger barbs seem to be quite content to chase around a dozen of their own kind and ignore the other fish. And of course a bigger tank can help reduce the effects of fin-nipping by giving potential victims fewer contacts with the aggressors. But the real secret of avoiding problems with fin-nipping is selecting companion fish that are either just as nippy, fast moving or that tend to hang out in a different area of the aquarium. For example, tiger barbs routinely pick on angelfish, but don't damage other barbs, can't catch most danios, and rarely run into the top-dwelling hatchet fish.
Here are some of the most common nippers and nippees:
The school bullies. In addition to the tiger barbs (in all their color varieties, including albino, blushing, green and black), only a few of the other barbs are likely to nip - most commonly the black ruby barb and sometimes the clown barb. (Rosy barbs, gold barbs and cherry barbs seem much more friendly.) Similarly, a few species of tetras are possible nippers, including red minors and Buenos Aires, while most are pretty harmless. In addition, some of the danios are occasionally accused of fin-nipping, although this never seems to occur if there are more than a couple of danios in the school.
The "you've got to be kidding" nippers. A couple of fish are actually pretty savage fin-nippers, even though their looks are totally deceiving. The puffers, who have both the physique and propulsion of little tugboats, do an amazing job of de-finning fish with their little parrot-like beaks. How they catch anybody is a mystery; maybe the victims don't consider these little water-balloons much of a threat and venture too near. Blind cave fish apparently compensate for having no eyesight by biting everything they bump into - which is pretty much everything. And finally, the diminutive bumblebee goby is remarkably adept at nibbling the tails off other small, slow-moving fish.
The "preview of things to come" nippers. A lot of fish that eventually grow up to be big, obnoxious brawlers start out life as small, obnoxious nippers. This would include most cichlids, including South Americans like Jack Dempseys, convicts and firemouths as well as most of the mbuna from Africa.
The "come and get me"s. I know it's not polite to "blame the victim", but a few fish seem to be just begging to have their pectorals pecked at, their ventrals ventilated. or their tails trimmed. Baby angelfish are classic examples: their long fin and slow movements make them likely targets. Most of the artificially "long-finned" fish, including fancy guppies, bettas, black tetras, and even fancy goldfish have much the same problem. Any of these fish can make excellent community tank specimens - but only if one takes care to avoid adding even remotely aggressive or nippy fish to them.
Freshwater and Marine Aquarium Magazine
Copyright © 1997 James M. Kostich