When you think catfish, more often than not, you think ‘food’. But the giant catfish of the world are large, lurking, and extremely voracious predators which often stalk smaller fish and invertebrates from the depths of the world’s various rivers and lakes.

Not all catfish are monsters; true monster cats inhabit the biggest and deepest bodies of fresh water of the world. The members of the family Pangasiidae, Pangasius or ‘shark’ catfish inhabit the Mekong river and include old favorites, the Iridescent or ‘Hammerhead’ shark (Pangasianodon hypophthalamus) and the Paroon or ‘Hi-Fin Hammerhead’ shark (Pangasius sanitwongsei). The most impressive member of this family is still be one of Asia’s biggest fish, the Mekong Giant Catfish (Pangasianodon gigas), which can grow to over 2 meters long.

Members of the family Siluridae, which are also called ‘sheath’ fish due to their resemblance to a sheath, are spread across various continents. Two of its biggest members can be found in Asia: the Wallago Attu and Wallago Leerii reside in the depths of the Mekong River; some can be found as far as India. Both are known to grow easily over a meter long and prey on almost anything. Their most impressive feature? Imagine thousands of needle-like teeth grabbing at prey as the fish pulls it into the depths of the water. Yet still, these don’t compare to the biggest Siluridae: the Wels Catfish, which inhabits the waters of North America. They grow to more than 10” (feet) in length and there are reports it has eaten pigeons, ducks, cats, and even dogs.

In South America, the most popular family of catfish is the Pimelodidae or the long whiskered catfish. Both the Red Tail Catfish and the Tiger Shovelnose, which are almost always available at your local fish stores, are from this family. The most notorious member is the Piraiba (Brachyplatystoma filamentosum). The Piraiba has been documented to grow to over 10 feet in length. Allegedly, in Brazil, a man was swallowed whole by a giant Piraiba. This fish has also reached our shores and there is at least one that is still kept by one of the most extreme hobbyists in the country.

Although relatively a very tolerant fish, catfish are still quite challenging to keep. They lack scales but produce a slime coat to protect their bodies. Shedding the slime coat is often an indicator of stress or something wrong with the fish.

They are also extremely voracious predators, eating almost anything that fits into their mouths. The bad thing about this is that they do not know when they have eaten more than they can handle. A frequent cause of catfish casualties is indigestion. Sometimes, when they are too full, they regurgitate their meals and foul up the water, causing the ammonia to spike; this is extremely lethal to all fish.

Keeping them in tanks also presents challenges; catfish are known as “Tank Busters” because, with extremely muscular bodies and hard heads, they can easily smash through aquariums. In my experience, a 2” red tail catfish easily smashed a standard 100 gallon aquarium. With that in mind, it is better if they are kept in ponds or extremely large-sized and thick-glassed aquariums that can withstand their tendency to bash their homes. A good filtration system is also a must as they eat a lot and produce much waste.

When it comes to tankmates, we have a simple rule: If it fits in the catfish’s mouth, it’s food. Thus, only equally big species may be kept with monster catfish. However, there are some catfish that can dislocate their jaws to accommodate bigger prey. Hence, keep in mind that anything you keep with a catfish is at risk. The catfish may accept it and live with it for the rest of its life—or it may see it as a meal.

Catfish are among the biggest freshwater fish; that’s why a monster fish collection wouldn’t be complete without them. However, due to their size and large appetite, special considerations and thorough research must be done prior to attempting to keep a monster catfish.

This story appeared in Animal Scene’s January 2016 issue.