Do Plecostomus Eat Other Fish?

Plecostomus fish are opportunistic feeders and scavengers. But do they eat other fish?

Apr 30, 2023bySara Payne
do plecostomus eat other fish

If a dying or dead fish sinks to the bottom of their tank, plecos will eat it. Another reason plecos may eat other fish in the tank is stress. Have you noticed the number of smaller fish in your aquarium dwindling? Do you keep hearing an aggressive splashing followed by one of your fish missing? If so, you may find that your Plecostomus is feeding on its tankmates.

Why do Plecostomus fish feed on their tankmates?

pleco mouth open

They are opportunistic feeders

Plecostomus originated in South America, and they are a type of suckermouth catfish. They are added to tanks for their beauty, but also because they do a great job cleaning the tank. These fish are omnivores, and feed on the algae that grow in your tank. However, they also need protein such as worms or pieces of shrimp.

Usually, if your pleco is eating its tankmates, it’s because the other fish are about to expire. Plecostomus are scavengers, and they will take food where they can find it.

They are hungry

Many new fish owners see the algae build up in their tanks, which can be unsightly, and as a solution, they buy plecos to clean it up. However, they do not realize that within a week, these efficient suckers will have all the algae cleaned off and will once again be looking for food.

After a pleco has finished off all the algae in your tank, it will need regular feedings in the form of algae tablets, squash, cucumber, and bloodworms or shrimp. These proteins help your pleco thrive and not seek out other fish as a meal.


They are stressed

Since new owners don’t know that Plecostomus fish need additional food, they can inadvertently starve their pleco fish. Starvation causes immense stress. However, other issues can cause your pleco to become stressed and lash out at other fish.

If you notice erratic swimming, changes in coloration, a slimy secretion on the skin, gasping for air, or scraping at the bottom of the aquarium, these are all signs that something is wrong with your pleco.

Here are some of the causes of stress in a Plecostomus fish:

  • Too much ammonia
  • Overcrowded tank
  • infection
  • Skin irritation
  • Poor tank quality

You should work to fix any of these issues right away or your pleco could die. In addition, this stress may cause him to act out. Plecostomus fish are not aggressive fish and they do not want to confront other fish. If yours is eating other fish, he is likely reacting to extreme stress.

What are the best conditions for a Plecostomus fish?

pleco rocks

Tank Size

Plecostomus at the pet store appears small, but they can grow much larger. Most people buy these fish without realizing they reach up to 12+ inches long. They need plenty of space and freshwater to survive.

An adequate-sized tank for a Plecostomus depends on the species. Smaller species could live in a 20-gallon tank, while larger ones need up to 75 gallons.

You should only put one pleco per tank for two reasons: 1) they can be territorial with other plecos, and 2) each pleco needs a large amount of water and space to thrive.

Water Quality

The quality of the water is essential in making sure your pleco is happy. Your tank should have a filtration system. The environment should have stable water temperature and quality, and you need to check the pH balance every week.

Every 2-4 weeks, you should change out 10-25% of the water and you should replace the filter once a month. Following these steps will make sure the water stays healthy and clean.

Hiding spots

Plecostomus are shy fish who like to hide, so you should provide them with plenty of space to shelter themselves. They will also enjoy live plants and pieces of wood, which can double as hiding spots and a food source. If a Plecostomus fish is thriving in the right conditions, it can live 10- 15 years.

How can you keep your other aquarium fish safe from a Plecostomus?

pleco bucket

Plecostomus fish are generally good tankmates. They do well in community tanks that are not overcrowded and that have gentle, peaceful fish. If your Plecostomus is being aggressive to its tankmates, you may want to test the water and observe the environment to determine what is stressing the fish. Some well-meaning owners think releasing plecos to local streams will solve the problem. However, plecos are not native to most regions and can become invasive species. These highly adaptable fish burrow into mud banks, devastating local environments.

In conclusion, if you suspect your Plecostomus fish is eating other healthy fish in your tank, you may need to check the water quality and meet your fish’s needs. However, plecos may eat other fish that are dead and dying simply because they are opportunistic feeders. These fish aren’t typically aggressive, but if owners release them into local streams, they can wreak havoc, so be sure you know how to care for your Plecostomus properly.

Sara Payne
bySara Payne

Sara is a mother of two and a high school English teacher who rediscovered her love of writing during the pandemic. She has 5 rescue cats: Neville and Luna, who are white cats with black and grey spots, and Ginny, Blue, and Fairy, who are calicos. Besides taking care of humans and fur babies, Sara enjoys gardening, crafting, and spending time in nature.