Name: Wolf Fish
Other Names: Trahira, Mud Characin, Tiger Fish, Tiger Characin, Tararura
Scientific Name: Hoplias malabaricus
Distribution: Costa Rica to Argentina in most rivers' basins
Water Temperature: 68 to 79 degrees Fahrenheit (20-26 degrees Celsius)
Diet: Adults love live fishes, while young ones take smaller live foods. They may be induced to take non-live foods, especially if the foods somehow give the appearance of being alive because of their movement through the ingenuity of the aquarist.
Water Chemistry: dH 4-25
Lifespan: I can find no references on this.
Species Description Ever thought about a skinny torpedo with teeth whose mouth is in an inferior position? Think about that again, and give it a drab coloring and black mottlings that seem to be in some sort of vertical linear pattern. Place a black eye near the front, a small ocellus near the rear, and give it some fins, all of which are clear with some light yellowish-brown coloration to the individual rays. Now if you give it a dorsal that has a small linear contact with the dorsal surface yet stands tall and a small black stripe going diagonally downward and backward from the eye, you have the form of a Wolf Fish.
Species Behaviour These nocturnal fish prefer to be fed at night. They hide until food appears and then swoop in to get their food as quickly as possible. They will, of course, adjust to your schedule, but that's not as fair as letting them live as they would in the wild. Be careful when moving around in the tank because they might just bite anything that moves. They grab their prey, shake it until it is stunned and then swallow it head-first.
They feel most comfortable if they can hide during the day.
This nocturnal nature and need for reduced light will hurt your chance of keeping plants alive in their tank. As if that wasn't enough reason to avoid keeping any plants with them, trahiras will knock loose plants in moving through the tank and will destroy any other decor that is not firmly in place.
Unfortunately, they seem to have an instinctual need to move to better waters and, on some primitive level, trahiras know that they can move overland because their swim bladder absorbs oxygen from the air. They will exit their tank when the "need" arises, so keep it covered completely!
One final warning -- trahiras are not too fond of conspecifics and may engage in battle royales if housed with their own kind or even congeners.
Natural Conditions Pretty much any type of habitat; FishBase cites the following as potential homes for Hoplias malabaricus: "...diverse habitats from free flowing clear water streams, well up into the valleys, to slow turbid waters, water courses, irrigation and drainage ditches, and ponds on the plains."
Natural Range Costa Rica to Argentina in most rivers' basins
Minimum recommended tank size 75 gallons
Water Temperature 68 to 79 degrees Fahrenheit (20-26 degrees Celsius)
Water Quality They do well in water with the following parameters -- pH between 6.0 and 8.0 and dH between 4.0 and 25.0.
Sexing Females have more girth than their male counterparts.
Breeding It is unlikely that these fish will be spawned in aquaria in captivity, but tropical ponds are possible breeding grounds.
Pairs build nests in shallow water (~ 12" in depth); these nests are basically depressions devoid of any debris. Females lay about 2,500 eggs over a 15 day period. Males guard the nest. Incubation takes four days and then the fry, which are 6-8 mm in length, can take small live foods.
Feeding Adults love live fishes, while young ones take smaller live foods. They may be induced to take non-live foods, especially if the foods somehow give the appearance of being alive because of their movement through the ingenuity of the aquarist.