So, you’ve just picked up a cute, small pleco from the local pet store, ready to see the algae disappear in your aquarium. The fish store sold it to you as the ideal, cheap solution for all your algae problems. In an almost magical way, all the algae will be gone in a matter of days… 

Unfortunately, a lot of misinformation is out there about the diet and behavior of pleco catfish. Bad pet stores want to make money and sell it to their customers, without giving information on how to care for them, or what they really need.

Caring for your pleco is much more than putting it in a tank full of algae and hoping it survives. Caring for plecos is fun, but they’re not the friendly cute algae-eating creatures you might think.

You might be thinking of getting a pleco to put in your tank and how it will affect the ‘nasty’ algae growing in it. No worries: after reading this post, you’ll have learned everything about plecos and their algae-eating behavior.

Do plecos eat algae?

When you think about plecos, the word algae almost immediately comes to mind. Algae-eater is a synonym of the common pleco and is often labeled as the solution to all algae.

There are many species of plecos that regularly eat algae. In the wild, these species will eat biofilm and algae. These plecos will thus eat algae and other biofilms as part of their diet. Young plecos will eat more algae and as the fish gets older, it might lose interest.

Plecos do eat algae, but you should always feed them extra food. Otherwise, they will starve. Depending on the species, feeding plecos vegetables or a varied diet is always a good choice.

What pleco species eat algae?

To give a complete answer to this, you need to know that ‘pleco’ is a collection of hundreds of species. These species differ in appearance, behavior, and diet. 

Most omnivorous and vegetarian species of plecos will eat algae. This includes bristlenose plecos, common plecos, and clown plecos. Carnivorous species like zebra plecos and snowball plecos do not eat algae.

In the wild, bristlenose plecos and young common plecos are mostly omnivores. This means that they will eat what comes around. In many cases, their diet consists out of algae and biofilm growing on wood and branches. As a result, you will need to replicate this diet by feeding plant-based foods.

On the other side, we see that there are carnivorous pleco species. The most common meat-eating species are Hypancistrus species, like zebra plecos (H. zebra) and snowball plecos (H. inspector). These will not eat algae and require a dedicated diet of high-protein meaty foods.

Keep in mind that not all species eat the same amount of algae. Some plecos have a natural diet consisting almost entirely out of algae, while others only occasionally eat algae.

To help you, I’ve created a table with the most common pleco species, and whether they eat algae or not.

Species / genus Natural diet Algae-eater?
Bristlenose pleco(Ancistrus sp.) Vegetarian, grazing on biofilm Yes, eats a lot of algae
Common pleco (Hypostomus sp.) Omnivore, mostly algae and some meat Yes, especially young specimens
Clown pleco (Panaqolus sp.) Grazing on wood, other plant-based foods Limited amounts
Flash pleco (Panaqolus sp.) Grazing on wood, other plant-based foods Limited amounts
Zebra pleco (Hypancsitrus sp.) Entirely carnivorous, shrimps, snails, ... No
Queen Arabesque Pleco (Hypancistrus sp.) Entirely carnivorous, shrimps, snails, ... No
Snowball pleco (Hypancsitrus sp.) Omnivores, mostly meat No
Leopard frog pleco (Peckoltia sp.) Omnivores, mostly meat No
Candy Striped Pleco(Peckoltia sp.) Omnivores, more meaty foods No
Peppermint pleco (Paracistrus sp.) Mainly algae Yes, good algae eater
Golden Nugget Pleco( Baryancistrus sp.) Mostly high-protein plant-based foods Yes
Sailfin Pleco (Pterygoplichthys sp. Brown algae, plant-based material Yes, especially brown algae
Royal Pleco (Panaque sp.) Mostly plant-based, ocasionally wood Yes
Blue phantom pleco (Hemiancistrus sp.) Omnivorous, a good algae eater Yes
Sunshine Pleco (Scobinancistrus sp.) Omnivorous, mostly meat No

The main difference between algae-eating and meat-eating plecos is their digestive system and basic anatomy:

Herbivores have a long digestive system, made for digesting long fibers and things like wood. Carnivorous plecos have a rather short digestive system and their mouth isn’t made for scraping off algae and wood. 

If you want to know more about what plecos eat wood, I suggest reading the article I just wrote on why plecos need wood. There might be a lot more benefits than you think.

As stated above, herbivore pleco catfish will have a different mount as opposed to meat-eating catfish. Meat-eating catfish will have a smaller mound, with less teeth. It’s made to suck up things, rather than to crape off.

The mouth of this Royal pleco is made for grasping on wood. Photo by Jan

What sort of algae do plecos eat?

Apart from the species, you will first need to determine the sort of algae you have in your tank. I will discuss the five most common sorts of algae, and whether you may expect your pleco to eat them.

  • Brown Algae (diatoms)
  • Brown algae often occurs in starting tanks. It will most likely fade away as the balance in your tank picks up.

    Most species will eat brown algae, but especially the Sailfin pleco seems to prefer brown algae.

  • Blue-Green Algae (Cyano Bacteria)
  • Blue-green algae are actually wrongfully called algae. It’s actually a bacteria that can do photosynthesis. BGA are sometimes even dangerous for humans, and in some cases animals die from drinking infected water. 

    Unfortunately, pleco fish will not eat blue-green algae, and there are no fish species known that doo eat it.

  • Blanket weed
  • Plecos will usually not eat this sort of algae. Mostly because it’s hard for them to eat algae not growing on flat surfaces.

    If you want to battle this sort of algae, shrimp are a better choice.

  • Beard Algae / Black Bush Algae
  • Beard algae are often considered one of the hardest algae to get rid of. Partially because not a lot of fish eat this sort of algae.

    Plecos will not eat beard algae. One of the only species that will eat this is the Siamese Algae eater. 

    A Clown Pleco resting on a bed of algae. Photo by Kai Schreiber

  • Green Algae
  • This is one of the most recognizable and most common kinds of algae and all of the algae-eating plecos will eat green algae.

    Does a pleco clean your tank?

    Another thing plecos are often sold as-is as the ideal cleaner for your tank. It will clean up leftover food and on top of that eat dead plants and algae.

    Plecos may actively eat algae, dead plants and make your tank appear cleaner. However, a pleco should never be bought to clean a tank, since they produce a lot of waste. Plecos can also be destructive, and it will be counterproductive keeping them for this reason.

    Why to not buy a pleco to clean your tank

    • Plecos are one of the biggest waste producers in the aquarium hobby. You will need to buy a strong filter and perform regular water changes if you want to keep it happy and healthy. This means that when not prepared for it, the pleco will cause more algae than removing it because the waste creates extra nutrition for the algae.
    • Another reason for not wanting your pleco as a cleaner is that they can be destructive and harmful to your plants. Especially common plecos are known to dig and sometimes even eat other fish.
    • There is no guarantee that your pleco will keep eating algae. Sometimes adult fish get tired of eating algae and will prefer regular fish food over algae.
    • An algae problem should never be solved by adding a live animal. It’s perfectly normal for every tank to have some algae, but if it’s getting out of hand, you should try to find a solution other than adding a fish, since it’s most likely the result of underlying problems in your tank.

    If you want a fish to clean your tank, there a numerous better options than plecos. Think about Ottocinclus catfish, shrimp, or snails. These species will produce less waste and will not be destructive.

    Pleco stopped eating algae?

    If your pleco stopped eating algae, it can be because of several reasons. Usually, young plecos will eat more algae than older specimens. It can also be because your pleco has become lazy because it has enough food. It is most likely not because it’s sick.

    The most common reason is that your pleco has become lazy. Just as humans, they don’t really like putting in too much effort. If you feed your pleco every day, it might just not feel the need to actively search for algae. 

    We also see that most young fish seem to care about eating algae. As they get older, many plecos will prefer easy higher protein food you give them. With common plecos, this is something that often occurs. They are sold as the ideal, small and cute, solution for your algae. Unfortunately, they will grow to be 15 inches and stop eating algae as they get older.

    Conclusion

    Many pleco species will eat algae since it’s a crucial part of their diet in the wild. They will mostly eat green and brown algae. The most common species that eat algae are bristlenose plecos, common plecos, and clown plecos. Zebra plecos and sunshine plecos will not eat algae.

    Pleco catfish are not the best way to keep your tank clean, and should never be bought only to do that. Better solutions are shrimp or snails.

    Recources