You may think you’re not super familiar with scavenger fish, heck, you might not even know what the term implies, but I’m certain you’ll be familiar with many species of fish that are, in fact, scavengers!
Bottom-dwellers such as catfish, eels, and eelpouts, as well as hagfish, lampreys, remoras, and even some sharks, are all types of scavenger fish. And although most fish are not scavengers, it’s good to get an idea of which ones are and what they eat (mostly dead or dying animals – ew), as adding some to your tank set-up could be a great call.
Scavengers are known opportunists – eating anything and everything they can get their fins on. In the wild, the majority of fish mostly live on a diet of algae, plankton, worms, and other fish and are usually defined as ‘Carnivorous,’ ‘Herbivorous,’ or ‘Omnivorous’ – but there are a select few species that feed entirely as scavengers.
Read on to learn more about these fish species, what they eat, and how you can house some of your own in your home aquarium!
What Is a Scavenger Fish?
A scavenger fish can easily be defined by exploring what they eat. In short, they scavenge and will eat anything they can get ahold of. Their diet in the wild may typically consist of the following:
- Dead or dying fish
- Dead slugs and snails
- Dead octopus and squid
- Dead sharks
- Dead sea cucumbers
- Dead crustaceans
- Drowned birds/animals that have fallen into the water (often whales, seals, polar bears, etc.
Scavenger fish may sound disgusting, but their eating patterns are essential in maintaining the environment by keeping the waters in which they live clean. They’re mainly bottom feeders, living off debris, dead fish, and algae on the plants and floor of their homes.
Adding scavengers to an aquarium can be a great investment. Their natural cleaning powers keep your tank looking shiny and fresh, reducing your cleaning costs and the time you need to maintain your tank – they do that for you. Think of them as little live-in maids for your fish!
In the wild, their diet changes between seasons due to the increase/decrease in deaths and increase/decrease in algae growth. Their diet also changes over the span of their lifetime. As they grow bigger, they can consume larger food and deter other scavengers that no longer threaten them.
Do Scavenger Fish Eat Other Fish?
Yep! As I’ve just explained, scavengers eat dead and decaying (or sometimes just dying) fish, which can be quite disturbing if you have them in a home aquarium.
Sadly, if you see your ornamental fish being nibbled at, it’s with good reason. Despite looking alive and healthy, scavengers only begin to eat other fish when they know they’re sick. On their way out, many people see a scavenger nibbling at their ornamental fish and think, “Oh no, Jerry is chewing Penelope to death!” In fact, Penelope was already sick to begin with.
As pet owners, we don’t often notice the early signs of sickness in our fish, and it’s very common for the other fish in the tank to know before we do. So if your tank mates seem to be getting along well, and one day one of them starts eating another, there’s a high chance it’s time to start saying goodbye – unless you do something about it immediately.
The scavenger fish in the tank know that a fish is sick long before we humans do due to their well-developed sense of smell. When a fish is sick, it begins shedding skin cells faster and producing more mucus as a biological way of getting rid of the illness (similar to how our nose runs when we’re sick). Scavengers smell this mucus, which attracts them to start eating sick fish.
This, in turn, stresses out the sick fish, slowing their recovery and, in many instances, making their situation much worse. After all, if your housemate came in and started chewing on your leg every time you caught a cold – you’d probably end up a lot worse off too!
So if you see a healthy fish being nibbled at by a scavenger in your tank, separate them to a solitary tank and begin treating them for illnesses. That way, your fish will be unbothered by scavengers, enabling them a safe and speedy recovery.
What Do You Feed Scavenger Fish?
In their natural habitat, scavenger fish prioritize the food with the highest nutritional content before they resort to eating less nutrient-dense foods such as algae. So, when kept in captivity, these omnivorous fish will eat the feed given to the tank before it even sinks to the bottom, before spending the rest of their day leisurely grazing on algae.
This algae grazing helps keep their tanks sparkly clean, which is why they’re commonly kept as aquarium fish and sold as pets which make a great addition to community tanks, but this doesn’t mean you don’t need to feed them!
Without regular food, any scavenger would also need to eat a lot (and I mean a lot) of algae to stay healthy. So if there isn’t enough residual food left floating around the tank for your scavengers to eat, they must also be fed regular food – whatever you usually provide the tank with should be fine, just make sure it has a high nutritional value.
How Big Do Scavenger Fish Grow?
There isn’t an exact answer to this question. After all, it completely depends on the fish. Let’s face it; a tiny little snail isn’t going to grow to the size of a Great White shark.
Okay, that’s a bad example – but it demonstrates how different scavengers can be, and this is no different when it comes to different species of scavenger fish too!
Can You Keep Scavenger Fish as Pets?
Of course! As I mentioned, many people add various types of scavengers to their home aquariums to keep as pets (or as their pet’s private cleaning crew!).
Some more common scavenger fish kept as pets are plecos, Clown loaches, the Corydoras catfish, and certain types of snails. If you’re an experienced fish keeper or familiar with the aquarium hobby, you’ll likely have heard of a few of these.
Which Types of Fish Are Scavengers?
Some types of scavenger fish you may already be familiar with, be that from a general knowledge of nature or from seeing them in the aquarium hobby!
Many scavenger fish, such as Cory catfish and Clown loaches, can be seen in tanks across the globe, sucking on the glass walls, plants, and rocks and eating debris.
That said, it’s time to delve into what types of fish are scavengers, both in captivity and in the wild.
The primary scavenger fish are:
Catfish are a type of bottom feeder that use their whiskers (barbels) to detect food on the floor of a body of water. They’re useful to their environment as they clean up their habitat and eat decomposing matter, such as dead plants and fish.
Many people are familiar with catfish being kept as pets due to a species called the plecostomus – More commonly known as a pleco! – Yep, if you didn’t know, they’re a type of catfish! These suckermouths are common in home aquariums because they are adorable and great at cleaning!
There are many types of catfish, but not all are kept as pets.
Native to the fresh waters of South America, the Loricariidae are also known as ‘Armored catfish’ – due to the armor-like plates covering their body.
With over 60 different species of Loricariidae, they vary hugely in size, with some able to grow to more than a foot in length.
Most kept as pets are typically smaller varieties, housed as part of community tanks to clean up dead plants and old food from the bottom, and can often be seen cleaning the glass walls of the tank with their little suction-cup mouths!
Another armored catfish species commonly kept as a pet is the Corydoras (or Cory catfish). These bottom feeders are also native to South American freshwaters, like the Loricariidae.
The similarities don’t stop there. They’re also popular aquarium pets due to their compact size and excellent cleaning abilities, and they use their barbels to detect food, vibrations, temperature changes, and predators!
Though they’re mostly scavengers, Corydoras’ will also happily consume plants, small insects, aquatic invertebrates, and other things they come across while sweeping the tank floor.
Saltwater / Marine Catfish
Unlike the other two species on this list, the Saltwater or Marine catfish are not commonly housed as pets, nor are they primarily scavengers. They grow far too big to be kept as part of a home aquarium and are omnivorous species, not only scavenging decomposing matter but also eating plants and algae and some live prey.
Most scavenging catfish are tropical freshwater fish, but saltwater species such as the Hardhead and Gafftopsail exist and are native to the Atlantic Ocean.
Another species known as an opportunistic feeder or scavenger is the shark. Granted, you won’t find many scavenger sharks in home aquariums, but their diet makes them truly fascinating – they’ll scavenge anything!
Sharks in the wild eat meat from animals that have died or are injured, such as dead or dying fish, whales, sharks, dolphins, and turtles, as well as sea birds, seals, and sea lions.
Scavenger sharks only like to eat fresh meat. The fresher, the better, so any carcass they come across isn’t left untouched for very long. Sometimes they like their meat so fresh that sick or injured animals become their primary target.
The hagfish is one of the scavenger species that isn’t very well developed. As it lives on the dark ocean floor, its eyes are barely functional, but its sense of smell is well-developed enough to sniff out food and find its way around.
Hagfish basically eat anything they can get their teeth into, and with their long, worm-like body, they sometimes can enjoy a meal by tunneling into a large carcass, eating as they go. A disturbing thought to say the least.
Other than larger animals and whales, they feed on dead squid, sharks, seabirds, and even other dead hagfish – they’re not picky if they’re resorting to cannibalism! This being said, they’re not one for home aquariums. The hagfish are native to coastal waters and are passive scavengers who eat almost anything they come across.
They can survive and function without food for up to 12 months! Which explains why when they find a larger carcass, they go at it like they haven’t eaten in months – because, most likely, they haven’t!
Hagfish are truly one of a kind and can only be compared to one similar type of fish, in particular, the lamprey.
Like the hagfish, lampreys are also prominent sea scavengers, feeding on anything they come across.
They dine in a similar way to the hagfish (yep, I know, another creature that likes to burrow into dead animals as it eats them!) – But you may be surprised to learn that they occasionally do something even weirder. The lamprey has a toothed tongue (yes, you read that correctly – a tongue with teeth on it!), which it attaches to its prey as it chews through it.
Lampreys are less eel-like than hagfish, though, and have more well-developed tail fins. Their mouths are also more defined, with many sharp teeth visible on their ‘lips’ and tongue. Again, I’m well aware that this sounds like a creature from a sci-fi movie, but I can assure you I’m not making it up!
Oh, look! Something we recognize again! A normal creature – no more sci-fi, tooth-tongued monsters!
Though some eels can be kept in home aquariums, you must remember that not all of these are scavenger species, so be sure to research their diet to provide the best care for any eel species you may take home as a pet.
An example of a scavenging eel species is the Snubnose, which eats the carcasses of other animals. However, they can also attach themselves to the bodies of larger fish and sea mammals to drink their blood – a bit like some kind of large sea-dwelling leech.
Eels, however, play a key role in their natural habitats as a general species. They’re both predatory fish and prey to many other creatures, so they are important in freshwater and saltwater food chains.
The remora is an interesting species of fish. Another common scavenger that isn’t housed in aquariums, remora attach themselves to sea creatures such as sharks in order to feed off of the scraps the sharks leave behind when eating. I personally like to call them a crumb catcher (my dog is one of those!).
Attaching themselves to sharks means not only do they get a relatively consistent supply of food but also free transportation and a friend! (Or, in reality, protection from predators).
In return for the free rides and bits of food, the remora helps its host, in this case, the shark, by keeping them clean and eating other parasites on them as well as skin, scales, and mucus.
Remora not only attach themselves to sharks but also turtles, boats, dolphins, and whales! They cling to their host using a suction cup on their upper body, and when without a host, they bumble along in the current until they stumble upon one.
What Scavengers Can I Keep as Pets?
Unlike the most common scavengers, mostly sea creatures, there are a few scavengers commonly found as pets, housed as part of a ‘cleaning crew’ in home aquariums.
- Otocinclus catfish
- Pictus catfish
- Asian Stone Catfish
- Doctor Fish
The Otocinclus catfish is a bottom-feeding scavenger that dwells at the bottom of freshwater tanks. An opportunist, the Otocinclus eats practically anything, including leftover food scraps, dead plants, dead animals, and algae. They prefer plant-based meals and usually choose dead plants over animal matter.
That’s how you can tell they’re spoiled for choice in captivity – They can choose to live a vegan lifestyle if they so wish!
Next, we have the extremely adorable Pictus! Even its name is cute! Adorable little fishies with beautiful long whiskers, the Pictus keeps your freshwater aquarium looking good by cleaning it and simply by existing in it!
Its pretty markings have earned it the nicknames “Leopard Corydoras” and “Polka Dot Corydoras.”
As the Pictus ages and grows, its diet changes over time, though it mainly scavenges for insects, crustaceans, and other small aquatic creatures that may be sick or dying. Adult fish, of course, can eat bigger things and have been known to eat smaller fish and tadpoles occasionally!
Asian Stone Catfish
The Asian Stone catfish is another great choice for a freshwater tank. These fish help break down dead animals, decaying plants, and erm “organic matter,” keeping the ecosystem they live in balanced and healthy.
I get super excited over the popular “Doctor Fish,” known as the Garra Rufa, popularised in the beauty industry as they eat human skin cells, usually from people’s feet.
I’ve never actually had these little guys nibble at my toes. Still, I’ve met them on several occasions in aquariums and aquarium cafes (yep! They’re a thing!) in South Korea, where they’ve attached themselves to my fingers and had a good munch.
And I mean a munch.
If this is something you’ve experienced, you’ll know that it just kind of tickles a little bit, and it feels like they’re very gently sucking at the skin. If you enjoy doing this regularly at the spa, you might not want to read this next part – just a warning!
When I said a munch, I wasn’t lying. Doctor Fish have something called “Dermal Denticles” – Rows of tooth-like structures which they use to scrape off the dead skin.
When kept in captivity, their diet consists mostly of dead skin cells, but in their natural environment, they’re a carnivorous species, eating anything from debris to small insects and vertebrae.
Yep, you heard me right! Goldfish!
One of the most common household pets (I’ve personally had a grand total of three over my lifetime), you may be surprised to find out that goldfish are scavengers too!
Even beginners know that goldfish commonly eat flakes when housed in captivity, and those who may have read up on goldfish care may know that their diet is usually supplemented with bloodworms and frozen brine shrimp.
Their diet in captivity should be well-rounded and highly nutritious in order to provide your pet with the best care possible, even though goldfish are known to eat just about anything (I’ve even seen one of mine eat his own poop before).
In this article, we have discovered some of the most important and notable scavenger species – both in the wild as well as in captivity, and discovered that a lot of them aren’t picky and will simply eat any dead or decaying plant or animal matter that they find floating around.
They all help to clean and take care of the environment in which they live, keeping their native ecosystems healthy and your tank sparkling clean.