Monster Cats

Author: Arthur Masloski

A cautionary tale of some catfish species aquarists may encounter in the aquarium hobby, but which should be avoided by most fishkeepers because of the monster sizes they can reach.

A Catfish for Every Purpose

The Siluriformes order is arguably one of the most successful orders of animals on this planet, and it’s also among the largest. Known commonly as catfish, there are about 36 families of these and about 3000 documented species. According to John Lundberg and John Friel of the Tree of Life web project (, one out of every 20 vertebrate species is a catfish.

Catfish range across the globe in both fresh and salt waters. They live in every conceivable habitat, from small clear streams to stagnant ponds, even in caves. Catfishes also have evolved to exploit every possible food source—some are predacious, some scavengers, and some herbivores. There are some that are parasitic, and there are some who specialize in eating wood. Their reproductive habits are equally diverse. Some show parental care, while some do not. There are even those that rely on other species to care for their young.

They range in size from some of the smallest vertebrates on the planet at 10mm (Aspredinids and Trichomycterids), to some of the largest, such as the Mekong giant Silurus glanis at 600 pounds. It is no surprise that catfishes are so popular with aquarists, given the diversity very briefly outlined above. Fish shops always have a wide selection of these fishes to choose from, and some like Corydoras are community staples. Others, like the banjo catfishes, are oddities to be marveled at. And still there are those presented to us that really have no business in the aquarium trade at all.

Cats to Avoid

Let’s look at the most commonly encountered catfish species that are suitable only for truly gigantic tanks, such as those you’d find at a public aquarium.

Channel Catfish

The channel catfish Ictalurus punctatus has been an aquarium staple for some time. Farmed extensively as a food fish in North America, they are also a native species in much of the continent’s waters. They belong to the family Ictaluridae, one unique to the North American continent, containing over 40 species. Despite their diversity, the channel catfish is likely the only member you will find in a fish store and is presented in both its wild and albino color forms. This is unfortunate, as the channel catfish is also one of the larger members of the family. The world record weighed in at 58 pounds and many are caught by fishermen in the range of 20 to 50 pounds.

Because they are so easy to obtain, many live in improper conditions, and some are even released into the wild. The practice of releasing any fish, native or not, is both illegal and dangerous to the wild ecosystem. Channel cats grow very fast, some aquarists reporting a size increase of about an inch a month. They are also known to eat just about anything, including tankmates, a trait common with many catfishes large and small.

The good news about these fish is their tolerance of cold water, which means they can live in ornamental ponds with the likes of koi and large goldfish. They become tame with relative ease and may even surface to feed on pellets. Their coloration ranges from an olive-yellow to almost black in larger adults; black speckles decorate the body of the fish. They have a deeply forked caudal fin that is edged in black on juveniles, and a typical catfish body, completely naked without any armor or scales.

Iridescent Shark

The name “shark” is one often associated with shark-like catfishes. Generally it is their appearance that gives them this label, but I assure you there are no species of freshwater sharks in the aquarium trade. These catfish, however, can reach a size comparable to many shark species. The iridescent shark Pangasianodon hypophthalmus is an Asian species, and like the channel catfish, it is raised in its native area as a food fish. Perhaps it is this factor that has made both so common in the aquarium trade.

Whatever the case may be, they are another aquarium staple and likely here to stay. These fish belong to the same family as the 600-pound Mekong giant catfish (Pangasiidae). They don’t reach quite that size, but at about 4 feet in length and about 100 pounds, they are monsters by aquarium standards.

Sold in both their wild and albino forms, they are active schooling fish. Because of their lifestyle they are even less suited for aquariums than some of the others in this article. Kept alone, P. hypophthalmus is a nervous fish that zips quickly around the tank when startled. When larger, this can create quite a problem. I have heard many stories about these catfish literally knocking themselves out during a standard tank cleaning, and have even personally seen it happen.

Should you have a desire for this fish—even with this information—there are certain steps you should take. An indoor pond is pretty much required, and a rounded one is your best option, as it improves the swimming space for these catfish and eliminates the problems corners can create with their behaviors. The system will have to be heated, and if possible multiple specimens should be kept. It is a huge undertaking, but that would allow for a much better life for this fish than the standard community system that so many end up in. The iridescent has a long naked body and is typically bluish or silver in color, but some are darker, almost black. They have very large eyes, small barbels, and a deeply forked caudal fin. Juveniles have two white stripes along their sides.

Colombian Shark

The Colombian shark Sciades seemanni is a member of the Ariidae family found along the coasts of Central and South America. In the wild it lives in the brackish waters of rivers and estuaries. Despite being a brackish species, it is almost always sold as a freshwater fish. It is true that while young they can survive in fresh water, but this eventually changes as the fish ages and salt becomes a necessity to successfully keep this species. If not provided with salt, the fish can become ill and suffer skin problems, and eventually will die. Salinity between 1.005 and 1.015 is best.

As for size, compared to others mentioned, it isn’t really a monster. They grow to a length between 1 and 2 feet, manageable but not something for a community aquarium. They range in color from silver to brownish, with a white belly. The pectoral, pelvic, and anal fins are black in color with white edges, giving the fish the common name silver- or white-tip shark.

Red-Tailed Catfish

I have had the good fortune of never meeting the red-tail catfish Phractocephalus hemioliopterus in a fish shop. The reason I say good fortune is because many other aquarists across the country have seen them, and claim it is quite common. This catfish comes from South America and can reach a size of 4 or even 5 feet in length.

As catfish go, it is a very attractive species. The tail of the fish is reddish orange in color, hence the name. The rest of the fish is black with a white belly and a white stripe running along its sides. In addition to the fish’s attractive coloration, it is also said to be an excellent wet pet. They are very interactive and responsive to their owners. Don’t let this fool you though; they will quickly kill and eat just about any fish you place them with, as there aren’t many fish that a 3-foot catfish can’t eat.

Common Plecostomus

Without a doubt, plecos are among the most commonly sold fish on the market, and it can be said that they are one of the most abused and neglected. There are several species sold as common plecos, but for the most part they are members of the genus Hypostomus, typically Hypostomus plecostomus. Other species, such as the sailfin plecostomus Glyptoperichthys gibbiceps, are often mistaken as a Hypostomus species and sold as such, but their requirements are similar anyway.

They all reach about the same size: between 12 and 20 inches. This may not sound like much, but given that this species is sold to so many aquarists in the country, it is an important thing to make note of. These fish don’t do well in small aquaria, despite being placed in them as janitors. And janitors they are not.

While they will eat uneaten food and some species of algae, they don’t eat fish waste and actually produce more waste than most species. They cannot be expected to sustain themselves on leftovers and algae alone, either. They are fish that enjoy eating and their diet must be well-supplemented. Algae wafers make a great staple, and foods such as blanched romance lettuce, zucchini, cucumber, and other vegetables should also be supplied. If their dietary requirements are not met, these normally peaceful fish can become a nuisance for other fish. In their search for food they have been known to suck on to the sides of other fish, feeding on their slime coat.

Plecos are great fish and are very interesting, so I am not trying to turn you off to them. Just keep in mind that they do require specific care: large setups, lots of filtration, and plenty of forage in order to thrive. Coloration varies a lot with individuals. Some are gray while others are brown, and others still are almost black. The body is covered all over with spots and blotches. They only have two barbels near the mouth, and an armored body. The dorsal fin is large and prominent when erect.

Paroon Shark

The paroon shark Pangasius sanitwongsei isn’t quite as common as any of the previously listed species, but is worth mentioning because it is said to be on the increase in fish shops. This species is closely related to the iridescent shark and quite similar in behavior. It is, however, a much larger animal., reaching about 10 feet in length.

Also available in the aquarium hobby is a short-body version of this fish. These specimens are becoming more common and are basically a short, fat version of their normal relatives. They are a bit drabber in appearance than iridescent sharks but look very much the same. Adults typically have extended filaments on their pelvic, pectoral, and dorsal fins.

Shovelnose Catfish

There are two species of catfishes available under the trade name shovelnose. Both come from South America and both belong to the family Pimelodidae. They aren’t fish-shop staples but show up on occasion. The lima or common shovelnose Sorubim lima is the smaller and more common of the two, reaching about 18 inches. The other is the tiger shovelnose Pseudoplatystoma fasciatum, which can reach a length of 36 inches or so. These fish are rarer and more expensive than the lima shovelnose, and their care can be difficult. They are sensitive to water quality and often difficult to feed. Typically, they require live food, but can often be trained to take frozen foods such as shrimp or squid.

Both fish have a similar body structure, a wide mouth that’s duck-like, long barbels, and long, slender bodies. The lima is grayish above and white below, with a black stripe running along the sides from the snout to the end of the caudal fin. The tiger is gray in color, with a white belly and vertical black stripes and spots along the body.

Ripsaw Catfish

This is a fish with many common names: black talking catfish, ripsaw, and mother-of-snails catfish to name a few. Scientifically, it is known as Oxydoras niger, and is a member of the family Doradidae from South America. I have had the opportunity to meet full-grown specimens of this fish, and they are quite impressive and tame. They even came to the surface for pellets and had no problem letting me touch their armored hides. In my opinion, they look like very large Corydoras with solid black coloration. They are generally a peaceful species, but they can reach about 36 inches in length.


As you can see, the saying “buyer beware” definitely applies to the hobbyist shopping around for a catfish, but luckily there is still an enormous variety of catfish to choose from. For more information on catfishes in general, I urge you to check out and For more information on the larger species, I suggest you visit the nice selection of forums on large and predatory fish that exist on the web.

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