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Do Plecos Eat Other Fish? (And What Fish Are Compatible with Them?)

Do Plecos Eat Other Fish? (And What Fish Are Compatible with Them?)

The purpose of this blog is to share general information and is written to the author's best knowledge. It is not intended to be used in place of veterinary advice. For health concerns, please seek proper veterinary care.

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Hypostomus plecostomus or the common suckermouth catfish are sometimes known as plecos to avoid the mouthful of their Latin moniker and the length of their colloquial name. There is quite a lot of anxiety among new aquarium owners who think that their plecos might be eating their other aquarium fish.

Hypostomus plecostomus or common suckermouth catfish (plecos) seldom kill and eat other fish. They are omnivorous scavengers, but occasionally, they may kill another fish if the living conditions are poor. Generally, the plecos only scavenge on an already dead fish in the aquarium.

Plecos are commonly found in fish shops and are frequently sold to new aquarium owners as the ultimate algae-eating fish to clean up their tank.

Why Do People Buy Plecos?

Pleco in an Aquarium

It is usually new aquarium owners that buy plecos. They start their fish tanks with great excitement and, after a few weeks, notice a lot of algae developing in their aquarium.

Algae is unpleasant to look at, makes it hard to see your fish, and if uncontrolled, will use up the majority of the nutrients and gases in the fish tank water. To get rid of the unwanted algae, aquarium owners go to their local aquarium store to ask for a solution.

The store owners know that this is going to happen, and they keep a stock of plecos ready for new fish owners. Plecos eat algae and can be very helpful in keeping the fish tank clean and free of algae.

Are There Different Plecos Species?

Queen Arabesque Hypostomus Pleco

The name pleco usually refers to the hypostomus plecostomus, which is the common suckermouth catfish. There are several types of fish that are sold as plecos at fish shops. They are all catfish belonging to the Loricariidae fish family.

The Loricariidae group of fish consists of about seven hundred described species and many undescribed species.

What Do Plecos Eat?

Leopard Cactus Pleco

Plecos eat algae, decaying plants, and wood, but they are omnivores, meaning they include some protein or meat in their diet. Worms or pieces of shrimp should be fed to your plecos to keep them healthy.

Your plecos will need additional food such as algae tablets, cucumber, and squash. Most fish tanks do not have enough algae to feed a growing pleco.

Do Plecos Eat Other Fish?

Green Phantom Pleco

Plecos seldom eat other fish as they are natural scavengers. They would much rather vacuum up some bits and pieces from the bottom of the aquarium than square off with another fish.

If you observe a pleco eating another fish, there is a high likelihood that the fish was dead anyway. Many new aquarium owners claim their pleco is killing and eating their other fish.

The reality is that the fish tank is unhealthy, and the fish are dying through the owner’s lack of knowledge. The pleco is scavenging and cleaning the aquarium.

If you see a pleco persuing and eating another fish, then there is a severe problem in your fish tank. Your pleco is malnourished or too large for the aquarium. A pleco killing another fish is rare and indicates that your pleco is stressed.

Are Plecos Friendly Towards Each Other?

Two Pleco in an Aquarium

While the pleco is young, it will get on with other plecos, but this situation changes when it matures. Plecos are territorial fish and do not like having other plecos in their territory.

A mature pleco will chase another pleco aggressively, but generally, this aggression is only shown to other plecos. This habit probably stems from a genetically influenced behavior that causes the pleco to defend its food sources.

The rule is that you should only keep one pleco per aquarium, which generally applies to all breeds of plecos.

Where Do Plecos Come From?

Plecos live in the wild in the rivers of South America, Panama, and Costa Rica. They generally prefer to live in fast-flowing shallow streams and rivers. They can live in brackish ponds or quiet estuaries. They are adaptable fish that will modify their behavior according to the environment.

Should I Get a Pleco?

Pleco Sucking on Aquarium Glass

Plecos are great for cleaning algae from your fish tank, but an enormous problem is they are fast-growing fish that quickly outgrow the fish tank. They can grow up to twenty inches (50 cm) very rapidly, which is far too big for most home fish tanks.

The problem arises when the aquarist has a massive pleco that does not fit into the fish tank. Pet or aquarium shops will not take the fish back as they sell many plecos and cannot take all these fish back.

The fish owner may decide to set the pleco free into the wild, thinking this is kindness. The issue is that the pleco’s adaptability allows it to thrive in these new environments.

Plecos compete with indigenous species and cause them to die out. They burrow into the mud banks, which causes the banks to collapse. The muddy, swirling water further compromises the indigenous species and results in abnormal geological changes to the waterways.

What Are Alternative Algae Eating Fish Instead of Plecos?

Otocinclus Eating Moss

There are many different Plecostomus species. Some of them are better adapted to life in a fish tank than the common suckermouth catfish. They do not grow as large and are usually easily accessible.

Bristle or bushy-nosed plecos grow to a maximum size of six inches. Clown Peckoltia or clown plecos are beautifully marked plecos that only grow to about three inches. They are highly territorial, so only keep one clown pleco per fish tank.

Otocinclus or otto cats are catfish from the same family as plecos. They are only about two inches in length and can live in small groups. They are much better algae eaters than the common plecos and so a much better choice for your fish tank.

What Fish Can I Keep With Plecos?

Plecos are generally compatible with most other fish, apart from their own species. They can be kept with smaller fish such as guppies, loaches, platies, mollies, gouramis, and hatchets.

Pleco in a Tank with a Cichlid

They can live with cichlids and angelfish, but the pleco needs to be the same size or bigger than the cichlids or angelfish to withstand their aggression.

Final Thoughts

Plecos only usually eat other fish if their environment is incorrect and they are not getting enough to eat. They are territorial and will attack other plecos and kill them if a second pleco is placed in the fish tank.

They often eat carrion and feed on dead fish. The fact that fish are dying indicates that there is a problem in the aquarium.

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