Forget piranhas; the wolf fish has acquired the monikers “Piranha Killer” and “Piranha Destroyer” among fishkeeping circles because of its reputation.

As I was about to write this article, I turned on the TV and tuned in to Animal Planet, where by coincidence, River Monster was coming on. In this episode host Jeremy Wade traveled to Brokopondo Reservoir in the remote jungles of Suriname where he interviewed a diver who was brutally attacked by a fish. The victim claimed the fish was the much-feared “Anjumara,” a little-known fish that is even more vicious and aggressive than the supposed flesh-eating piranha. The Anjumara is the wolf fish. It is one of the more popular fishes that monster fish collectors all over the world aspire to own. Wolf fish are South American freshwater fishes belonging to the genus Hoplias (H).

Currently, there are eleven species of wolf fish: H. aimara, H. australis, H. brasiliensis, H. curupira, H. intermedius, H. lacerdae, H. malabaricus, H. microcephalus, H. microlepis, H. patana, and H. teres.

The most popular among them is the H. malabaricus since it is the most commonly available in the market. But the biggest and baddest among them all is H. aimara. When the natives refer to the “Anjumara,” which evokes fear in them, without a doubt, they are referring to H. aimara.

The H. aimara is more commonly called the Giant Wolf fish or Giant Trahira (as Trahira is another local name for Wolf Fish). The word “Giant” is emphasized since H aimaras are known to reach over a meter in length with the largest ever captured at 1.2 meters long and weighing 40 kilograms.

First described by French zoologist Achille Valenciennes in 1847 from specimens collected in French Guiana, the H. aimara is present across most of the northern parts of South America, Brazil, Columbia, Venezuela, Guyana, French Guiana and Suriname, including Rio Tocantins, Rio Xingu, Rio Tapajos, Rio Jar, and Rio Trombetas, and is also found in coastal drainages in the Guyanas, Suriname, and state of Amapa, Brazil. H. aimara lives in habitats that range from large rivers, rapids, waterfalls, and flooded forest floor environments.

Tankkeeping H. Aimaras

H. aimaras are very hardy and tough fishes. They are tolerant of poor water conditions, as long as extremes are avoided. One will not encounter difficulty in keeping them. A pH range of 6.5 to 8 should be comfortable for them. Tropical temperatures of 23°C to 30°C are recommended. In my experience, the H. aimara often hurts itself, and it does so in many ways: they get cuts and bruises when they crash into driftwood when chasing prey; tear their fins when they hit the brace or glass cover; or bust their lip when they hit the glass panel.

They are injury-prone in captivity because of their reckless and violent behavior. However they are also tough, so they easily recover from these injuries in few days, even without treatment. The aquarium for H. aimara will have to be large since it is a very large fish. Remember, it grows to over a meter in length in the wild. In captivity, the H. aimara can easily reach 50 centimeters (cm). This should be considered average sized. It is highly probable that larger specimens will attain sizes of 80 cm. and up if the tank is large enough.

I have a friend, Joely Cervantes who saw a huge H. aimara in Malaysia. This was from a private collector and it measured 34 inches in length! Joely claims its head was bigger than his own, and its body girth was almost the same size. The aquarium will also need to have a good filter because the H. aimara can be a messy eater. It is not a choosy or picky eater as it will gladly eat any live or fresh meaty food. However, with its massive jaws and sharp teeth, it will surely mess up what it is eating. Scales and bits of meat will be scattered everywhere; thus, strong filtration is essential.

Also bear in mind that commercially available filters will not work. H. aimaras are known to attack anything in the tank, whether alive or inanimate. Thus, it can easily dislodge filters, tubes, airstones, etc if these are not fully secured. The tank for H. aimara will have to be well planned. Nothing must come loose, because if anything does, you are not going to recover it without getting bitten.

The Ferocious Fish

By the way, it is a common sight for the tanks of H. aimara keepers to have glass covered with algae. That’s because they can’t clean their tanks. The H. aimara is so ferocious it attacks even magnetic glass cleaners. I once asked for a picture of my friend’s 20-inch H. aimara, and I got a pic of an aquarium with lots of algae and a fuzzy image of a large fish behind the front glass panel. He told me the maid refuses to scrub the glass panels for fear of getting bitten. I have an 8-inch H. aimara and even at that small size, tank maintenance is beginning to be a concern. Every time I dip in a hose to siphon off tank water, the H. aimara attacks it.

When I remove excess food that he has not eaten using a net, he attacks the net. This is one fish that is always in a foul mood! The H. aimara has a bad temper because it is highly territorial and aggressive. When you approach an aquarium with an H. aimara, you will notice it flare and expand its operculum, much like male Bettas do. This is to show aggression and its fighting stance. When Joely saw that 34-inch H. aimara in Malaysia, he was amazed by its huge size but admits he was scared despite it being inside a massive tank. “I got scared because the fish really wanted to bite me.

I get the same feeling when you’re passing through a street and a large dog keeps barking at you,” shares Joely. This aggression will prevent you from ever finding a tankmate for your H. aimara. Any fish will surely be eaten. I believe the only fish you can put in a tank with an H. aimara are tiny ones that prove to be too small for them to bother with. However, any fish that is big enough to be a meal will surely end up as one. So I guess Neon Tetras with a meter-long H. aimara should be a good biotope aquarium.

Final Advice

The H. aimara is a legend in its own right. However, this is not for your average aquarist, but for the advanced fish collector. It is rare and not cheap, and may cost you an arm and a leg if ever you find one. To be able to enjoy it, one should have the means and commitment to provide a huge tank with adequate filtration system. Big fish can destroy things and create havoc inside the aquarium.

They can even break the glass. So for H. aimara keepers, their tanks must be built tough and all potential problems identified and addressed before even purchasing an H. aimara. Keeping an H. aimara requires a different level of responsibility. The fishkeeper will have to be committed to its special needs. If these needs are met, then the H aimara will provide a different fish experience altogether―an experience only the much-feared “Anjumara” can provide.

Distinguishing Characteristics

Hoplias species are similar in appearance and identifying them can be tricky. In fact, more often
than not, fish hobbyists post pictures of their fishes to ask for positive identification of the species they have.

Aside from the large size that H. aimara attains, it is in subtle differences visible only to the highly observant that one can identify a true H. aimara.

• Like most in the genus, H. aimara has an elongated cylindrical body shape. It develops a massive body as it grows older.

• The base body color may be light brown to dark grey with a number of generally thick vertical
patches or stripes. However, this base color and pattern may vary from each type of locality of the H. aimara.

• The head of the H. aimara appears to be bigger and wider than most of the species.

• The eyes of the H. aimara appear bigger, especially when it is young, and these are not clear
but rather, can best be described as “wall-eyed”.

• The teeth, like with all species in the genus, are impressive, jagged, and large.

The Key Distinct Features (KDFs) to look for that will help in positive identification of an H. aimara are:

• Small spots that are visible on the upper front portion of the body and on the head; and

• A vertically-elongated dark spot on opercular membrane or edge of the gill plate.

This appeared in Animal Scene’s June 2015 issue.