An artificial assemblage of small and medium-size South American tetras. Includes the genera: Acestrorhynchus (Pike Characins), Charax, Cynodo, Hydrolycus, Priocharax, Rhaphiodon, Roeboides.

(Excerpted from: Extreme Characins  Part 2: Wolves, vampires, and other horrors by Neale Monks)    

Payara: the vampire-tetra!

Where the wolf-characins were adapted to life in sluggish streams and pools, the family Cynodontidae contains a small number of species that are exclusively found in clean, fast-flowing rivers. All have robust teeth and among scientists these fish are called dogtooth tetras, but the two species offered to aquarists are usually called vampire-tetras on account of their protruding fangs. The two species sold appear to be Hydrolycus armatus and Hydrolycus scomberoides, though many retailers treat them as one and the same thing. The two fish are broadly similar: big, silvery, very streamlined and powerful, and with distinctly upturned jaws. Hydrolycus armatus is smaller (potentially getting to around 60 cm/24" in length) whereas Hydrolycus scomberoides can get to twice that size, but otherwise the only obvious difference is in the shape of the dark marking behind the gill covers. On Hydrolycus scomberoides this marking is approximately circular, whereas on Hydrolycus armatus it is a short, oblique bar.

It is actually quite debatable whether vampire-tetras are good aquarium fish.  They are obviously very big fish, and both require perfectly clean and well-oxygenated water, so frequent water changes and generous levels of filtration are the order of the day. Water chemistry requirements are typical for Amazonian whitewater fish: a neutral to slightly acidic pH plus low to moderate hardness. In the wild vampire-tetras are often found in groups, but in captivity when kept in small groups they are antagonistic towards one another, to the point that the dominant specimen eventually bullies conspecifics to death. On the other hand, single specimens often seem to be nervous and when scared will throw themselves around the tank frantically, damaging themselves in the process. Realistically, you probably need to keep a group of at least six specimens to stand anything like a good chance of the group forming a stable, happy school. Obviously setting up a tank for six active fish the size of vampire-tetras isn't something to be done on a whim. In addition, any tankmates from other species should be chosen with care. Placid armoured catfish would be ideal tankmates, but anything too aggressive, such as large cichlids, would be unwise.

As far as food goes, these fish are out-and-out piscivores. Vampire-tetras feed on schooling characins in the wild (including piranha!) and in captivity are most easily reared using live foods such as earthworms, river shrimps, and clean feeder fish. They can be weaned onto dead foods, such as silversides and lancefish, though this does take time. One final note: although these fish are fairly widely sold and seem to settle into aquarium life quite easily, they do not seem live nearly so long in captivity as in the wild. Many aquarists find that these fish do well for six months of a year, and then die for no obvious reason. Diet, water conditions, and their schooling behaviour may all be key factors, and any aquarist attracted to these fish should research them fully before bringing them home.

Freshwater barracuda, family Acestrorhynchidae

Freshwater barracuda have become quite common imports in recent years. Despite their name, these fish are not true barracuda but characins in good standing. All the currently known species are in a single genus, Acestrorhynchus, of which more than a dozen species are known ranging in size from 7 to 40 cm/2.75-15". Unfortunately for the aquarist, the more commonly traded species seem to be the bigger species rather than the smaller. In particular, Acestrorhynchus falcatus (27 cm/10.5") and Acestrorhynchus falcirostris (40 cm/15") seem to predominate.

As their streamlined shape and powerful jaws might suggest, these fish are predators, and that's the problem: these fish are not easily weaned onto anything other than live foods. Earthworms, river shrimps, and other robust invertebrate foods are preferred, though small prey like bloodworms may be taken as well, depending on the size of the fish. Despite their predatory nature, most species of freshwater barracuda are nervous and do best kept in a small group in a spacious aquarium with plenty of swimming space and plants around the edges. Floating plants, or at least plants with long, trailing leaves, such as giant Vallisneria, are greatly appreciated. Tankmates need to be chosen with care as freshwater barracuda are easily frightened.

Freshwater barracuda are often confused with the African pike Hepsetus odoe, an only-distantly related characin. Hepsetus odoe are big fish in the wild, getting to around 70 cm/27" in length, making them far from ideal aquarium fish. They are also exceptionally powerful fish with a very nervous disposition, and can easily damage themselves when alarmed by throwing themselves against the glass of the tank. Though barely suitable for maintenance in a home aquarium, these animals to make outstanding exhibits in public aquaria where they have space to settle in more comfortably.

Chuck, Neale... do you recognize this Ostariophysian?   6/10/09 Bob,  <Neale> This is one of the large Neotropical predatory characins, likely Brycon or Salminus spp.; my guess would be Salminus brasiliensis. These are big (up to 100 cm) predatory but not aggressive species that should be kept in large groups. In small groups (less than six) individuals may become aggressive towards weaker specimens. Can be mixed with large, peaceful but robust tankmates; Arowanas, catfish, etc. Jumpy, so need to be kept in a covered aquarium. Piscivorous in the wild, but happily consume earthworms, river shrimps, etc. in captivity; will take frozen foods, even pellets once acclimated. Not really viable as a home aquarium fish, but a superb species for public aquaria.  Forgive my brevity here; it's just gone 6 AM, and I need to get my skates on to catch a train!  Cheers, Neale <Thank you so much Neale. I do believe you're spot on. BobF>