Related FAQs: Ctenoluciid Fishes

Related Articles Characiform Fishes, 

/The Conscientious Aquarist, /A Diversity of Aquatic Life

The Pike-Characoids, family Ctenoluciidae,  In Aquariums

Boulengerella maculata pic by NealeM

Pike-characins, family Ctenoluciidae  (Excerpted from: Extreme Characins Part 1: Hatchets, pikes, and other lethal weapons by Neale Monks)    

Like the hatchetfish, the pike-characins are peaceful South American characins that inhabit open waters and stay close to the surface at all times; but there the similarities end. These fish are schooling predators that view smaller fish as food. They are fairly frequently offered for sale as oddball fish though, and in the right aquarium, can make excellent community fish. As is often the case with specialised predators, these fish are not aggressive at all, and actually want pass their time unnoticed by other fish so that they can more easily creep up on their prey.

Just as with hatchetfish, when scared, these open water fish instinctively jump or dash about the tank. While that may be helpful in a river or lake, in an aquarium these fish can end up damaging themselves. Injuries to the snout in particular are common and often become infected, leading to the death of this fish. Keep pike-characins either among their own kind or in a community tank with peaceful tankmates such as plecs or large barbs. Besides being easily frightened by aggressive tankmates, pike-characins will also panic if the lights come on too suddenly over the aquarium, especially if the room is dark. On the other hand, floating plants seem to calm these fish down, and tall plants around the edge of the tank, such as Vallisneria and Amazon swords, help to keep these fish from slamming into the glass when alarmed. If you’re going to keep these fish, you do need to plan ahead, and choose plants and tankmates with care.

There are two genera in the Ctenoluciidae, Ctenolucius and Boulengerella, between which seven species are known. Boulengerella lateristriga is perhaps the one most frequently sold, though under a variety of names including striped pike-characin and striped gar. It is usually sold at an appealingly small size, around 15 cm/6" being typical, but this fish can reach a maximum size of 26 cm/10" when fully grown (reports of larger specimens appear to be misidentifications). None of the pike characins are “easy fish” and the striped pike-characin is no exception. It needs a large, mature aquarium with excellent filtration and frequent water changes must be carried out to ensure that the nitrate levels are kept low. Soft, slightly acidic water is preferred, and likely essential to long-term success. Certainly, very hard and alkaline water should be avoided.

Feeding these fish is another headache. In the wild these fish are predators, taking insects when young and small fish as they mature. Since all the fishes sold are wild-caught, weaning them off live foods and onto frozen substitutes will be a major hurdle. Earthworms, mealworms, crickets, and other such foods will work as either a stopgap or a permanent diet, and it is definitely important to get your specimens feeding properly as soon as they are introduced to the aquarium. Once settled in, silversides and lancefish can be used effectively. These fish are crepuscular hunters, meaning that they are most likely to accept food at dawn and dusk. As with many other fish of this type, they hunt by sight, lunging at flashes of silver or white. Tossing a defrosted fish into a strong current of water within the tank usually does the trick, by fooling the pike-characin that the target is alive. Starving the pike-characin for a day or two does no harm if you want to whet its appetite, but do bear in mind newly imported specimens will likely not have eaten a proper meal for several weeks.

The spotted pike-characin, Boulengerella maculata, is broadly similar but a bit bigger, getting to about 30cm/12" in length.

Ctenolucius hujeta is known variously as the hujeta, the rocket gar, and the blunt-nosed gar (this latter name on account of its slightly upturned snout). Aquarium specimens can reach a trifle over 20 cm/8", though wild fish are said to get to more than twice that size (though as with Boulengerella lateristriga, some of these giant specimens may in fact be misidentifications). Ctenolucius hujeta is silvery-green in colour with a prominent dark spot on the base of the tail. Water chemistry and quality need to be similar to those required by Boulengerella spp, but on the whole Ctenolucius hujeta has proved to be a bit more amenable to life in captivity, and has even been bred in aquaria.

A closely related species, Ctenolucius beani, is superficially similar but larger species, getting up to 28 cm/11" in length. It is distinguished from Ctenolucius hujeta by being covered in dark blotches when young and small dark spots arranged in neat rows as an adult. Care is otherwise identical. All the pike-characins are sometimes sold as freshwater barracudas, though in fact that name is more properly applied to a completely different family of characins, the Acestrorhynchidae, a fascinating group of characins of which more will be said next month!

Pike characins indeed very pike-like in shape, but like the needlefish they like to form schools and mostly hang about it midwater rather than hidden among the plants. Boulengerella lateristriga is the most frequently sold species, most often as the “striped gar”. It reaches eight to ten inches in length and is strikingly colored, being basically silvery-brown but with a thick dark band along both flanks and mottled fins. Soft, slightly acidic water is essential, and low nitrate levels seem to help as well. Ctenolucius hujeta, also known variously as the “hujeta”, “rocket gar”, and “blunt-nosed gar” is another commonly traded species. It is silvery-green with a prominent dark spot on the base of the tail.

Basic care for these fishes is similar to the needlefishes: plenty of swimming space, good water quality, no aggressive tankmates, and floating plants to help them feel secure. Apart from small fish, pike characins will happily take chunky live foods such as mealworms, crickets, and earthworms. They can be weaned onto a frozen food diet fairly readily. They hunt at dusk and dawn, and seem to be attracted by a sudden flash of silver. If you throw a piece of whitebait into a water current at the right time of day, with the aquarium lights turned low, with any luck your pike characins will strike. Starving a healthy fish for a day or two will do no harm and does help to whet their appetites, but before training these fish in this way, make sure you fatten them up on live foods for a week or two beforehand. Newly imported fishes can be very underweight.

Predatory fish, large or small, add an interesting touch to any community tank, and if you don’t want to feed them live fishes, you don't have to, as most will happily accept all sorts of substitutes. Indeed, a good argument can be made for weaning them onto an alternative diet anyway, not least of which is the risk of transferring parasites from feeder fish to your pet fish. What makes these pocket-sized pikes so special are their subtle, stealthy habits and their sleek appearance. Miniature hunters they might be, but they’re still natural born killers!