Siamese Algae Eater Care Guide: Types, Size and More…

The Siamese Algae Eater may not be as popular as other algae eaters, but it is renowned as the single most efficient algae cleaning fish in the hobby.

They will eat up the algae that grows in a freshwater tank. From red algae to hair algae to the dreaded black beard, this fish will eat it all!

However, the is a lot of confusion about the fish because of all the different species.

Do you want to learn more about this algae eater?

Read on to learn about the different varieties, their size, how to care for them and much more…

Siamese Algae Eater

What is a Siamese Algae Eater?

Crossocheilus oblongus

The name Siamese Algae Eater refers to algae eating fish in the Crossocheilus genus.

Crossocheilus oblongus is the most popular, however Crossocheilus langei, Crossocheilus siamensis, Crossocheilus atrilime, and Crossocheilus reticulatus are all commonly known as Siamese Algae Eaters.

These species are so similar that they are often confused for each other. However, they all have the same basic care requirements.

They are native to Southeast Asia and are particularly abundant in Thailand’s Chao Phraya river and its tributaries.

Siamese Algae Eaters are best known for their algae eating. They are highly recommended for beginners who have run into their first algae problem. It is a great first defense against nuisance algae and is much safer than using algaecide.

A specimen in good condition can live for up to 10 years and will grow between 5 and 6 inches long.

These fish are quite sought after, so they can be hard to find. When you do find one you can expect to pay about $5 to $10 per fish.

Key Facts:

  • Experience Required: Freshwater fishkeeping.
  • Nicknames: None.
  • Color Forms: Silver, brown, tan, or yellow with a single black stripe.
  • Size: 5-6 inches.
  • Tank Size: Minimum 20+ gallon.
  • Tank Temperature: 75-80°F.

Pros and Cons


  • One of the best algae eating fish.
  • Very active.
  • Clears moss and plant overgrowth.
  • Extremely helpful for planted tanks.


  • Can damage aquarium plants.
  • Hard to identify the species.
  • Cannot be bred in home aquariums.

Siamese Algae Eater Appearance

Siamese Algae Eater Eating Algae

These fish are shaped like tiny jet planes.

This aerodynamic body shape is designed to help them swim through strong currents.

Unlike most other fish, they do not have a swim bladder. So they must stay in constant motion to remain afloat and a streamlined body shape helps them with this.

All species have two small barbels on their upper lips, with the Red Algae Eater having the longest barbels. The barbels help them detect tiny prey scuttling around in the substrate. They also help detect shifts in water pressure and even chemical changes.

They have a pointed or slightly upturned snout, and a sucker mouth that lets them graze on algae. They have six fins and they are all translucent and colorless.

You will find their triangular dorsal fin first. Then a pair of pectoral fins which sit just below the gills, followed by a pelvic fin on the abdomen. Their anal fin sits in between the pelvic fin and the V-shaped caudal fin at the end of the tail.

They are sold at about 2-2.5 inches long but can reach a maximum size of 5-6 inches.

As for their colors they are not much to look at – their plain colors allow them to blend in with the rocks. Most species are a silver color with a single black stripe from head to tail. Other possible colors include reddish brown, tan, or tawny yellow.

It is not possible to tell the difference between males and females until the fish is 3 years old. Even then, the only tell is the size (females are slightly larger and wider than the males).


There are several species of Siamese Algae Eaters, and it is very difficult to tell them apart. Here are the most common species available for aquariums:

  • Crossocheilus oblongus: This specimen is yellow or brown and has a slightly upturned snout and a straight upper lip.
  • Crossocheilus langei: Also known as the Red Algae Eater, this is the most efficient at cleaning algae. It is reddish brown with a light colored underside and a single dark band that runs from its head to its tail.
  • Crossocheilus siamensis: The True Siamese Algae Eater is one of the hardest to find. It has a silver body with a very thick black stripe, a sharply pointed snout, and a V-shaped upper lip.
  • Crossocheilus atrilime: This species eats more moss than algae. It is smaller than the other species by about an inch, and comes in tan or yellow.
  • Crossocheilus reticulatus: The Reticulated Algae Eater is solid silver, brown, or yellow with no black stripes.

Siamese Algae Eater Vs Flying Fox

Siamese Algae Eater Vs Flying Fox

The Siamese Algae Eater and the Siamese Flying Fox look so alike that they are often confused.

Flying Foxes are darker and have two black stripes instead of one single band. These black marks extend to the Flying Fox’s fins while the Siamese Algae Eater’s fins are clear and colorless. Though it can be difficult to see, the Flying Fox also has slightly longer barbels and tiny flaps on both sides of their mouth.

Siamese Flying Foxes are much more aggressive and territorial, and are more likely to bully other fish when placed in a community.

6 Fun Facts About Siamese Algae Eaters

  1. In addition to the Flying Fox, there are two other algae eating fish that are similar to this one: the Chinese Algae Eater and the False Algae Eater. False Algae Eaters are almost identical to this fish, while the Chinese Algae Eater looks very different and is much more aggressive.
  2. Black beard algae is one of the hardest types of algae to manage, but the Red Algae Eater can clear it away with ease.
  3. They are known for fin nipping so you should avoid keeping them with Gouramis.
  4. Because of their body shape, some hobbyists will call it a freshwater shark.
  5. The species are so similar that even retailers often cannot tell which is which.
  6. In addition to algae many of these fish can also assist you with trimming your plants and keeping your mosses and shrubs tidy.

Habitat and Aquarium Set Up

Crossocheilus oblongus on leaf

These fish are native to the Chao Phraya river.

They inhabit areas with rocky substrate that they can easily blend in with. The water is clear and the sunlight is strong enough to grow both plants and algae. Mosses, liverworts, and leafy plants are a staple of an Algae Eater’s habitat.

Since they do not have swim bladders they rely on currents to keep them afloat. Most of the time they remain close to the riverbed.

You will need a 20 gallon tank to keep just one of these fish. If you want to keep more than one then you will need to add 10 gallons of water for each additional specimen.

The water temperature should range from 75-80°F, with a pH from 6.0-7.0, and a water hardness of 5 to 18 dGH.

Your filter must generate a moderate current. A canister filter is the best kind to use as it will both generate a current and cycle the large amount of waste these fish produce. The light intensity should mimic that of the sun but should come from a bulb rather than direct sun exposure. Aim for 5 watts per gallon for 12 hours a day.

A hood will also be needed to stop them from jumping out of the tank.

Layer the bottom of the tank with soft sand under smooth, light colored pebbles. These fish do love rocks, but it is important to use only soft materials that will not cut their barbels.

A warm water temperature, high light intensity, and abundance of available surfaces will encourage algae to grow in quickly.

Rocks, logs, and natural wood will also encourage algae growth.

You should wait until your rocks and glass turn green before you introduce the Algae Eaters to their new home.

The perfect plants for this aquarium are those that can attract fine layers of algae – Java Moss is one of the best.

Hornwort can be used as both decoration and a supplementary food source. Pellia and Peacock Moss make great carpeting and can attract thin layers of algae too.

The wider the plants’ leaves are, the more algae they will attract.

Caring for a Siamese Algae Eater

A Siamese Algae Eater

These fish are not particularly susceptible to any diseases.

A strong filter, algae, and a clean tank is all this fish needs to thrive.

Because they lack a swim bladder they rely on currents and perpetual movement to stay afloat. Your filter must generate a current for the fish to travel along. You must also provide enough space for this fish to be able to stay in motion at all hours of the day.

Do not overcrowd the tank with too many plants or decorations.

Feeding and Diet

Even though this fish is called an algae eater, it cannot live off of algae alone. Algae should only make up a portion of its diet and not the entire thing.

In the wild Siamese Algae Eaters will eat small live prey along with plants, algae, carrion, and biofilm.

Within your aquarium you will need to give it flakes or pellet foods that are high in vegetable content. Use quick sinking flakes that are made especially for bottom dwellers.

If your tank is low on algae then you can use algae wafers or Spirulina tablets as a supplement. You can also offer boiled spinach, broccoli, or cucumbers as treats.

Live prey and meaty foods should only be given in moderation (once or twice a week) – too much of it can cause digestive issues. Brine shrimp, insect larvae, and bloodworms can be given live or frozen. If a pesky worm or bug makes its way into the tank then this fish will gobble it up before it can make a nuisance of itself.

These fish can be a little destructive when they munch on the plants in your aquarium. You can reduce this by offering them a few leaves and stalks cut from your plants.

Here are all of the different things that this fish is able to eat:

  • Algae
  • Biofilm
  • Plant material
  • Fish flakes
  • Bottom feeder pellets
  • Spirulina
  • Algae wafers
  • Bloodworms
  • Brine shrimp
  • Insect larvae
  • Carrion
  • Spinach
  • Broccoli
  • Cucumbers

Underfeeding is easy to do if you assume that it can only eat algae.

Most of the time they will find food on their own so you should only offer outside food once per day. Meals should be small enough for them to finish in 2 minutes or less.


Siamese Algae Eaters are always in motion but will usually remain close to the bottom of the tank.

They can swim very quickly and even make some impressive leaps!

You will often spot them climbing the walls of your aquarium, sucking up the algae that grows on your glass. This is how they reach the middle and upper areas of the tank.

Sleeping fish tend to prop themselves up on plants and let their tails swing back and forth even while their upper body is still. If it stops moving at all, it will sink to the bottom of the tank.

If you keep these fish in groups then they will attempt to assert dominance over each other.

While they may fight in smaller groups they will shoal peacefully in moderate to large numbers. You should keep at least 5 to a group.

Tank Mates

Group Of Siamese Algae Eaters

These fish can be kept in communities but some varieties are better kept on their own.

The True Algae Eater for example is a little more territorial and easier to keep with its own kind.

However, there are a few companions that will pair well with any species.

The Cory Catfish and the Kuhli Loach are two of the only bottom dwellers that can pair safely with these fish.

While freshwater sharks are generally not advisable, the peaceful Apollo and Roseline Sharks are two exceptions to this rule.

Danios (including the Giant Danio and the ever-popular Zebra Danio) of all kinds will get along very well. In addition to these, you can add Mollies, Guppies, and Tetras. You can pair this fish up with Nerite Snails, Amano Shrimp, and Ghost Shrimp to create an unstoppable algae cleaning crew.

As for what you should avoid, there are some things that may surprise you.

You may have heard that Algae Eaters can live with Gouramis. In reality they are likely to nip at the Gourami’s fins.

Pictus Cats and Plecos should be avoided as they may be in competition for the bottom territory.

Chinese Algae Eaters and Siamese Flying Foxes should not be kept with Siamese Algae Eaters as they are much more aggressive and are likely to pick a fight.

Finally, avoid Cichlids and territorial freshwater sharks like the Red Tail.

Keeping Siamese Algae Eaters Together

Keeping these fish together can be a little tricky because there are so many different species. However, they will be much more comfortable if they can live in a group.

Species such as C. siamensis are a little bit pushier than others. Whereas C. oblongus and C. langei are capable of living together in perfect harmony.

Since it is so difficult to tell which is which, you will have to monitor your group for any conflicts. Separate the group if you notice any fights breaking out. You can tell your fish are getting along when they begin to shoal together and when they are not rushing each other or fin nipping.

Can You Breed Siamese Algae Eaters?

There are many reasons why breeding Siamese Algae Eaters is not recommended.

Perhaps the biggest reason why is that it is too difficult to tell the different species apart. Different species cannot interbreed except in rare cases or if the breeding is done through artificial means. Furthermore, identifying characteristics do not show up until the fish is at least 3 years old.

Also, their natural breeding conditions are not well known so it is almost impossible to replicate them in an aquarium. What we do know is that they make spawning migrations that coincide with the dry seasons. They will make their way to the driest part of the stream to lay their eggs. Again, this can be hard to simulate in captivity.

While they are known to be egg scatterers, their clutch size, gestation period, and the care requirements for the larvae and fry are still unknown.

There have been no reports of successful breeding in home aquariums.

Successful attempts have been made at commercial farms using hormone injections, pheromones, and artificial insemination. The equipment required for this is expensive and difficult to obtain at home.

Siamese Algae Eater History and First Sighting

Crossocheilus oblongus was the first species to be discovered in 1823 by Kuhl and van Hasselt.

This genus entered the pet trade by 1931 and this is when the confusion between the species began.

C. siamensis and C. langei specimens were often labeled as C. oblongus, or vice-versa.

After the 1980s the existence of C. siamensis as a species was under debate. Some ichthyologists think that the species referred to as C. siamensis is really C. oblongus.

There is also some controversy as to whether or not C. oblongus really exists in home aquariums. Some do not believe this species entered the pet trade at all, and is really just a mislabeled C. langei.

This confusion continues even till this day and may never be settled.

Even scientists have difficulty telling them apart.

Quick Species Summary Table

Siamese Algae Eater
Other Common Names:
Scientific Name: Crossocheilus spp
Family Name: Cyprinidae
Distribution: Southeast Asia
Size: 5-6 inches
Color: Silver, brown, tan, or yellow with black stripe
Care Level: Easy
Temperament: Peaceful
Lifespan: 10 years
Minimum Tank Size: 20 gallons
Tank Mate Compatibility: Peaceful community fish


The Siamese Algae Eater is not the most remarkable looking fish but it is certainly one of the most helpful.

When unmanageable algae rears its ugly head, Siamese Algae Eaters are here to help. It will eat all kinds of algae from the tiniest particles to the thickest hairs.

Although there is a lot of confusion about the different varieties, it does not generally matter which species you have as they all eat algae.

It can live by itself but will be at its best when in a group.

Your aquarium will never be boring with these energetic critters around.

Has your Siamese Algae Eater solved your algae problem? Let us know in the comments section below…