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Tropical Fish - Catfish are bottom-feeders

Updated on June 16, 2012

The Catfish are scavengers

Catfish get their name because most species have whiskers on their mouths. Correctly referred to as barbels these organs are used to help them find food and as sense organs.

There are very many species of catfish that are kept by tropical fish hobbyists and many of them are thought of as bottom-feeders and scavengers. And indeed this is the method of feeding for a lot of types but others have sucker-mouths and graze the algae off rocks and plants.

Catfish such as the South American Corydoras catfish are frequently kept in community tanks because they are peaceful little fish that get along well with other types of tropical fish.

Corydoras paleatus

Peppered catfish (Corydoras paleatus)
Peppered catfish (Corydoras paleatus)

Corydoras cats

There are many species of Corydoras that are commonly kept and 142 species in the genus. The name Corydoras comes from the Greek "kory" meaning helmet, and "doras" meaning skin. This refers to their strong scales like armour.

The most commonly kept Corydoras, or "Cory" as they often called is the Bronze Corydoras (C. aeneus). The females reach around 2¾ inches and the males are smaller. This catfish has a pinkish body with dark blue-grey on the back and head and a metallic green-bronze on the sides. They can live as long as 10 years and are peaceful fish ideal for a community tank.

This Corydoras and other species have unusual breeding habits. Several males will court a single female and do not fight. The female will drink sperm from a male's genital opening. This she passes right through her on to her eggs which she can lay in another location attached to the leaves of plants.

Bronze Corydoras catfish are best kept in groups of five or more. They like to move about in the company of others of their own kind.

The Bronze Corydoras and related species are able to breathe atmospheric oxygen. If the water they are in is low in this gas they dash to the surface to take a gulp of air.

Another commonly kept species is the Peppered Corydoras (C. paleatus).

Upside-down Catfish

The Upside-down Catfish really does swim that way a lot of the time. There are several species known as Upside-down Catfish but Synodontis nigriventris is the most commonly kept. It comes from the Congo Basin in Africa.

This unusual fish grows to about 4 inches in length. It has large eyes and three pairs of long barbels. Its back is lighter in colour than its stomach because it spends most of its time the wrong way up. It is thought these fish evolved this way because they often feed on the undersides of submerged trunks and branches and swimming this way made it easier for them to do so.

The Upside-down Catfish is a peaceful fish that is well-suited to the tropical fish community tank.

Upside-down Catfish

Glass Catfish

Glass Catfish (Kryptopterus species) in Himeji City Aquarium, Japan. Copyright OpenCage.
Glass Catfish (Kryptopterus species) in Himeji City Aquarium, Japan. Copyright OpenCage. | Source

Glass Catfish and Ghost Catfish

The Glass Catfish (Kryptopterus bicchiris) is a very unusual catfish that comes from Asia and is often confused with the smaller but very similar Ghost Catfish (K. minor).

These weird fish get their names because of their transparent bodies. Only the head section, internal organs and the bones have much in the way of any colouring.

The Glass and Ghost Catfishes are also unusual as types of catfish because although they have barbels around their mouths they are most certainly not bottom-feeders. The Glass Catfish and the Ghost Catfish swim in the mid-levels of the water and like to be in shoals. They feed mainly on live food but can be trained to eat flake and other food types.

The Ghost Catfish grows to around 3 inches and can be kept in community tanks but not with aggressive species, and it is best if kept with others of its species.

Banjo catfish

Banjo Catfish

The Banjo Catfish (Bunocephalus verrucosus) is a personal favourite of mine. These strange fish look like almost like dead leaves and they can play dead too if disturbed. At other times they can move fast and will bury themselves in the sand or gravel to get away.

Banjo Catfish of which there are actually many species come from the Amazon region and other parts of South America and get their name from their body shape which is similar to that of the instrument they are named after.

These catfish are bottom feeders and resemble living vacuum cleaners when feeding. They are omnivores and scavengers but need some live food in their diets. Banjo Catfish mainly come out at night. They are peaceful and suitable for the tropical fish community tank.

Walking Catfish

Walking Catfish (Clarias batrachus)
Walking Catfish (Clarias batrachus)

Walking Catfish

The Walking Catfish (Clarias batrachus) doesn't have legs but it can and does make its way over the ground in an effort to find new ponds and waterways to call home. In fact in many places it has become regarded as a problem invasive species because it does this. This is the case in several of the Southern States of the US.

The Walking Catfish, which comes originally from many countries in Southeast Asia, grows to around 12 inches in length. It can breath atmospheric air and as long as it keeps moist can survive out of the water for some time.

The Walking Catfish is a typical catfish with long barbels around its mouth and it feeds mainly on the bottom. It is an omnivore but will readily eat smaller fish and other aquatic animals.

Various other species in the Clarias genus get sold to tropical fish enthusiasts as well. Many types of Clarias Catfish come from Africa as well as Asia,


Plecostomus on glass by JohnstonDJ
Plecostomus on glass by JohnstonDJ | Source


The Plecostomus ,or "Pleco" as it is often called, is any one of many species of sucker-mouth catfishes that are often sold as "Algae-eaters." The most commonly kept and well-known species is Hypostomus plecostomus. This species has been introduced into some parts of North America including Texas and Florida.

Although it is usually sold at just a few inches long it can grow to a massive 2 foot in length and is really a fish for a large aquarium. Very big Plecos are often in show-tanks in tropical fish stores.

There are very many related species and some new ones are still being discovered in South America where the fish are found. The Plecostomus Catfishes all have a mouth with which they can suck algae of a smooth surface and attach themselves to it. They have armoured bodies with tough scales and eyes that can be rolled with the eye-sockets.

The Plecostomus is generally peaceful when young but they can become aggressive when much bigger. They can also uproot `plants in an aquarium.

All species of Plecostomus eat a lot of algae and vegetable matter but are really omnivores and scavengers that will eat other fish foods too.

Although most species of Plecostomus are a dark brown colour with black spotting there are some types that have spectacular black and white colouration. At least one type has a coloured eye as well.

Some species of Plecostomus develop bristle-like growths on their head by their mouths too. These are more correctly known as species in the genus Ancistrus and are known as Bristlenose Catfish species. The armour-plated look of thei bodies of all these types of sucker-mouth catfish gives them a very prehistoric look as well.

Hand tamed Plecostomus

Otocinclus Catfish

The Otocinclus (Otocinclus affinis) is a distant relative of the Plecostomus and in the Loricariidae family of sucker-mouth catfishes. There are 18 species in the genus Otocinclus and all are small fish that come from South America.

They will eat algae off the sides of a tank and browse on stones and the leaves of water plants. Being small catfish with the the largest type not reaching more than 2 inches, the Otocinclus species should not be kept with much larger fish that could bully or even eat them. They like company of their own species and can be kept in a community tank with other compatible and gentle species of tropical fish.

Like many types of catfish the species of Otocinclus are able to breathe atmospheric air and can gulp this at the surface of the water.

Electric Catfish

The Electric Catfish (Malapterurus electricus) can really emit an electric shock, and as much as 350 volts have been recorded given off by these fish. The Electric Catfish is definitely not for the community tank!

These fish grow to around 3 foot in length and are predators. They stun the smaller fish and aquatic animals they eat with electric shocks. They also use this system to defend themselves.

The Electric Catfish, which comes from Tropical Africa and in the Nile and region, is one for the specialist tropical fish-keeper. It needs a very large tank.

The Electric Catfish will also pull up plants and shift gravel about so can really make a mess of an aquarium lay-out.

Electric Catfish (Malapterurus electricus) female

Other catfish

There are many other species of catfish including ones that can be kept in cold freshwater and brackish and marine species. The European Wels Catfish (Silurus glanis) can grow to over 2 metres in length and live to around 30 years.

These massive catfish will eat other fish, frogs, mice, rats and eve take ducks. They live in rivers and lakes in many parts of Europe and arr one of the largest freshwater fish.

Catfish come in many shapes and sizes, some of them attractive to look at and others decidedly ugly. Most types have a whiskery mouth and are aptly named as catfish!

Copyright © 2011 Steve Andrews. All Rights Reserved.


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    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      Thank you for your comments, Teresa! If I didn't have a cat and wasn't living in an apartment that isn't really suitable I think I would have a tank again too!

    • Teresa Coppens profile image

      Teresa Coppens 

      8 years ago from Ontario, Canada

      another great animal hub. Love the read! You have inspired me to start a fish tank again. I find nothing more relaxing than watching a peaceful fish community.

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      Thanks for your feedback!

    • profile image


      8 years ago

      Thanks for sharing this great hub on cat fish, I didn't know too much about them before reading your article. The cat fish in our local lakes are called mud cats and are pretty good eating. We also have cat fish lakes where some enjoy spending hours catching stocked cat fish, some get pretty large. Just for the record I'd rather eat one than catch and clean one.

    • Wesman Todd Shaw profile image

      Wesman Todd Shaw 

      8 years ago from Kaufman, Texas

      Read on! Many a case in which one had to be surgically removed from the human urethra!

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      As it says here it is "alleged": and I quote: "Although lurid anecdotes of attacks on humans abound, very few cases have been verified, and some alleged traits of the fish have been discredited as myth or superstition."

    • Wesman Todd Shaw profile image

      Wesman Todd Shaw 

      8 years ago from Kaufman, Texas

      Well, it's true that The Candiru can not defy the laws of physics, what it will do should it get the quite enough thank you!!!!!!!!!

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      I have heard that the Candiru is more of a scary story than a reality when it comes to what it is said to do! have a look on Wikipedia.

    • Wesman Todd Shaw profile image

      Wesman Todd Shaw 

      8 years ago from Kaufman, Texas

      There's so many varieties that it's astounding! Here in North Texas, there's several that we fish for food regularly.

      In South America, around where the Rio Negro meets the Amazon...lives one of the scariest fish in the world, The Candiru....a species of catfish.

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      Yes, it is something I would love to do again that used to give me a lot of pleasure!

    • homesteadbound profile image

      Cindy Murdoch 

      8 years ago from Texas

      I to could easily go back to keeping fish. It was a very neat hobby to have. I liked having different cats in my tanks also. And I am fond of the plecostomus.

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      Thank you! I have just published Hub 23 and am on my 17th day so doing well!

    • brittanytodd profile image

      Brittany Kennedy 

      8 years ago from Kailua-Kona, Hawaii

      Great hub! This one is very informative and interesting. I loved the upside down catfish (and video). It cracks me up to watch them swim like that. So cool. Thanks for sharing, voted up, etc. Keep up the great work in the challenge (30in30)!

    • Bard of Ely profile imageAUTHOR

      Steve Andrews 

      8 years ago from Lisbon, Portugal

      Thanks for posting, Talisker! If I had my own place and the money I could happily go back into keeping fish again!

    • Talisker profile image

      Honor Meci 

      8 years ago from UK

      What a fascinating read! I used to have an upside down fish, although I don't know whether it was intentional (on his part) He was one of those fish that look as if they've been cut in half with a magnificent tail stuck on its end. (As if to cover the halfness)

      Fish are fascinating little beasties, although I'm much more partial to enjoying them in other people's fish tanks these days.

      A great hub!


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