Hydrolycus scomberoides
The tetra vampire or Hydrolycus scomberoides is naturally widespread in the upper and central Amazon River in Brazil, Bolivia, Ecuador and Peru. Adults keep their fish in shallow streams and juveniles mostly in shallow channels and areas of submerged forest. During the breeding season, which runs from November to April, tetras vampires make long upstream migrations in large flocks. These fish are suitable for very large aquariums, so they are not often found in aquarists' collections.
Hydrolycus scomberoides is very similar to the Pajara (Hydrolycus armatus), but the latter is significantly larger and not found in aquarists' home collections. Despite this, the two fish are often confused. The tetra vampire has a massive body. The pelvic fins are in the shape of swallow's wings. The dorsal and anal fins are displaced to the side of the root of the tail plumage. Anal plumage is broad. The lower jaw of the fish is studded with small, sharp teeth, and also contains a pair of sharp fangs that precisely enter the special holes located in the upper jaw when the fish closes its mouth. The entire structure of the fish indicates that it is a predator. The maximum size of the fish in the wild is 45 cm, while in aquariums it usually does not exceed 25 cm.
The Hydrolycus scomberoides is a very aggressive fish and should preferably be kept alone or with non-aggressive fish of larger size, as this tetra is actually quite peaceful with those fish that are too large to become food for it. Can be kept in a group of 3 - 5 individuals, but in this case the aquarium must be a volume of at least 1000 liters, which in domestic conditions is already very problematic.
Young individuals most of the time swimming "head down" and all the time hiding among the decorations, while adults are usually in the normal position.
Ideally, the aquarium should be set up like a running stream or river by running the outlet nozzle of the water filter along the back wall or using an aquarium pump for water flow. A mixture of sand, fine and coarse gravel can be used as substrate. Place large, smooth stones and snags on the bottom. Plenty of space away from decoration is required to allow the fish to swim freely. The aquarium with these fish can do without plants.
Water parameters: temperature 24-28° C, hardness dH 2-15° acidity pH 6,0-8,0. Need filtration, strong aeration and a weekly change of up to ½ of the aquarium water with fresh. Pisces have high demands on water quality and do not tolerate the accumulation of organic matter.
The aquarium should always be covered, as Hydrolicus mackerel is an excellent jumping fish. Furthermore, it is advisable to cover the back and side walls of the aquarium to make the fish less fearful.
As with an overwhelming number of predatory fish, the tetra vampire should not be fed with mammal or bird meat such as beef heart or chicken. Likewise, you should not feed them with goldfish for a long time. They are very often at risk of catching various diseases and are of low nutritional value if they are not prepared well in advance. Newly purchased specimens often refuse to eat anything other than live fish, but they can gradually become accustomed to fish meat, shrimp, mussels, earthworms, etc. feed the fish once a day.
Reproduction
Hydrolycus scomberoides do not breed in an aquarium. Any fish that occasionally appear in the trade are imported from their natural habitat.
