Siamese Algae Eater: Species Profile

Category: Catfish

Common Names: Siamese Algae Eater

Scientific Name: Crossocheilus oblongus

Family: Cyprinidae

Minimum Tank Size: 20 Gallons

Care Level: Easy

Temperament: Peaceful

Max Size: 6 Inches

Temperature: 75-80 F

pH: 6.5-7.2

Tank Level: Bottom

Colors: Tan, Black, Yellow

Diet: Herbivore

Breeding: Difficult

Siamese Algae Eater on Gravel

Siamese Algae Eater Species Overview

Siamese algae eaters won’t win an award for their beauty, but they’re valuable fish in many tropical aquariums because of their cleaning abilities.

These fun-to-watch fish get along well with other tank mates and are relatively low maintenance. So, they’re a great fit for beginner fish keepers.

Distinguishing Features

Siamese algae fish have a plain appearance and a standard fish shape—a long body and small fins without any unique designs.

However, they have two small rostral barbels, giving them the appearance of having a mustache.

There’s little variation in colors and markings among Siamese algae fish; most have a light grey to gold color.

They also have a thick black stripe that runs from their mouth to the tip of their tail on either side of their bodies.


You might not guess it by looking at them, but Siamese algae eaters belong to the carp family, a common species in Asia.

The Siamese algae eater, in particular, comes from two basins in Southeast Asia—the Chao Phraya and Mekong. They’re also native to the Malay Peninsula.

These bottom-dwelling fish don’t have swim bladders, meaning that when they’re not moving their fins, they sink to the bottom of the sandy substrate, where they thrive.

It’s common to encounter Siamese algae eaters in freshwater streams and rivers. You might also see them perusing through flooded forests during monsoon season.

Siamese algae eaters can live in cloudy water, although their algae-eating ways help clean the water where they live.

Siamese algae eaters live in places with lots of plants in the wild. Algae is their preferred plant, but they also like java moss and other plants for hiding and eating.


Both male and female Siamese algae eaters grow up to around six inches long in captivity.

However, females have a girthier appearance and weigh approximately 30% more than males when they reach adulthood (three to four years old).


Siamese algae eaters have a tremendously long lifespan of up to ten years.

That’s significantly longer than many other species of tropical fish. Of course, the quality of care you provide your Siamese algae eaters significantly impacts their potential lifespan.


It isn’t easy telling male and female Siamese algae eaters apart, as you can’t determine their gender from color or markings.

Instead, you’ll need to rely on the shape of the fish. Females tend to have wider bodies than males, particularly around their bellies.

The issue for the casual fish keeper wanting to breed Siamese algae eaters is that it can sometimes be challenging to see this difference until the female fish reaches three or four years of age.


There’s little need to worry about your new Siamese algae eaters disrupting the peace in an already established aquarium; these fish are notoriously peaceful.

Siamese algae eaters enjoy living in a tank with other fish mates of both their same and different species.

While you don’t have to worry about Siamese algae eaters being aggressive towards other fish in your tank, if you have fish with a mean streak, it’s vital to give your algae eaters a place to hide. That’s because they lack a swim bladder and rest on the bottom of tanks.

However, Siamese algae eaters sometimes unintentionally cause issues in a tank because they love to swim around so much. Therefore, ensuring your tank is large enough for your fish to spread out is essential.

As for within their species, there are usually few issues between Siamese algae eaters. But males can sometimes get territorial, particularly when preparing to mate.

Siamese Algae Eater Eating from Rock

Tank Parameters

If you’re ready to be the proud owner of Siamese algae eaters, it’s vital to understand the tank parameters these fish require. Doing so will help you keep your fish healthy for up to a decade.

Minimum Tank Size

The Siamese algae eater requires a minimum of 20 gallons per fish, although it’s best to offer them 25 to 30 gallons.

They’ll appreciate the largest size tank you can manage, given how much they enjoy swimming around in search of food.

Water Parameters

Getting the water conditions set up in your Siamese algae eaters’ tank before you bring them home is an essential step in being a responsible fish keeper. These fish don’t offer much room for error with their ideal parameters.


Siamese algae eaters need warm water that remains between 75°F to 79°F.

That’s a small range compared to what many species of tropical fish can tolerate, which leads us to this point—make sure that your Siamese algae eaters have compatible water parameters with any tank mates that you may wish to introduce into their aquarium.


You should keep the pH of your Siamese algae eater’s water between 6.5 to 7.0. These fish err on the side of enjoying acidic water, but not to the extreme.


As freshwater fish, Siamese algae eaters don’t need copious amounts of salt to survive. But adding a little aquarium salt on occasion can help improve their immune system.

Furthermore, you may need to add salt to their water if they come down with a parasitic infection or disease. In either case, placing your Siamese algae eaters in a full-out saltwater tank is a sure way to kill them.

Siamese Algae Eater Eating Plant on Light Colored Rock

Tank Setup

Let the fun begin! Once you have your tank and understand what kind of water your Siamese algae eaters require, below are some ways to spruce up their aquarium and keep your fish healthy.


Sand is the best substrate for Siamese algae eaters. Not only does that mimic the substrate they’re used to in the wild, but you don’t have to worry about it scratching their bellies.

That said, it’s safe to include small, smooth gravel as a substrate. The key is to ensure that whatever you use for your tank’s bottom isn’t sharp.


Siamese algae eaters need lots of hiding places, so including functional decorations in their tank is crucial. We love using hollowed-out logs and creating rock formations with crevices for our algae eaters.

Again, make sure the decorations you choose have smooth surfaces. Your Siamese algae eaters will use them for sleeping and hiding, so you don’t want decorations scraping their bodies.


Your Siamese algae eaters will be thrilled if you include plants in their aquarium, given that they love to eat them and use them as hiding spots.

So this is the part that gets tricky—if you sense your Siamese algae eaters are looking too plump for their own good, replacing live plants, like java moss, with artificial plants might be the healthiest choice.

In addition to putting some live or artificial plants in their tank, your Siamese algae eaters will love dining on the algae they find naturally growing around their tank.

Some fish keepers even occasionally place an algae wafer in the tank to ensure their fish get enough of the food they love.


Scientists have discovered that fish have circadian rhythms like humans, meaning they rely on external factors like the sun to know when they should be awake and asleep.

For this reason, setting an aquarium lamp over your tank is crucial. Ideally, the light should have a timer so that you don’t have to worry about forgetting to turn it on or off.

Depending on your point of view, another advantage of an aquarium lamp is that it encourages more algae growth. That’ll thrill your Siamese algae eaters, although it shouldn’t be at the expense of too much algae growth in the tank.


A high-quality filter system is essential for any tropical fish aquarium, regardless of the species you have. Even though Siamese algae will eat algae in your tank, many other toxins they don’t eat will build up and kill your fish if you don’t have a filter.

Ideally, your tank should have a biological, mechanical, and chemical filter. Be sure to check the filters regularly and change them according to the instructions on the package.


A heater is an absolute must for Siamese algae eaters, given that they have such a low tolerance for temperature changes.

When you purchase a heater, it’s also important to pair it with a thermometer. The best way to monitor the water’s temperature is by leaving the thermometer in your tank so that you can check the temperature when you feed your fish.


Per their name, Siamese algae eaters love dining on algae. But it’s not the only type of food they eat.

These fish happily munch on other vegetation. They’ll even chow down on insects and dead fish in the wild.

So, below are some foods you should incorporate into your Siamese algae eaters diet:

  • Pellet fish food
  • Algae wafers
  • Brine shrimp
  • Bloodworms

Since Siamese algae eaters have a near-constant food supply via finding algae in their tank, you don’t need to overdo feeding them.

You should feed them at most once or twice per day and monitor how much they eat in two or three minutes. Then, remove the remaining food.


Breeding Siamese algae eaters without the proper equipment and knowledge is challenging. For starters, it’s difficult to tell the males and females apart.

But the other issue is that most of these fish require hormones to instigate their mating instincts, making them a better fit for professional fish breeding farms.

The bottom line is that if you’re interested in fish breeding, give up the hope of doing so with Siamese algae eaters. Many other species of tropical fish are prolific breeders, making it easy on people new to the breeding space.

Lerdsuwa [CC-BY-SA-3.0]

Common Diseases

Siamese algae eaters are prone to the same diseases as many other species of tropical fish. The good news is that you can prevent many diseases by following the best care practices we covered here.

Nonetheless, illness can still strike. Below are some of the most common diseases your Siamese algae eater might face.

Swim Bladder Disease

Swim bladder disease is a known trigger among scientists in carp fish. Unfortunately, many issues can cause it, making narrowing down the problem challenging.

Even though Siamese algae eaters don’t have a swim bladder, you’ll know they’re suffering from it if they have buoyancy problems. Most notably, they won’t be able to remain upright at the bottom of their tank.

Reasons for swim bladder disease may include constipation, eating too fast, and gulping air.

Fin Rot

Fin rot is a fungal or bacterial infection that affects the fins of Siamese algae eaters. The fins often develop white edges and become stringy.

It’s common for fin rot to occur due to poor water conditions. Therefore, you should immediately perform a partial water change.

Treating the tank’s water with an antifungal or antibacterial medicine is also important.

Bacterial Infections

The Siamese algae eater’s fins aren’t the only part of their body that can encounter a bacterial infection. Unfortunately, there’s no shortage of bacteria strains that can affect freshwater fish.

Your algae eater may have a bacteria infection if they show signs of cloudy eyes, bloody patches beneath their scales, or open sores.

Treating their water with an antibacterial medication and making frequent water changes is vital to treat this condition.


Dropsy occurs when Siamese algae eaters have a fluid buildup in their bodies. It commonly occurs from a liver issue.

If your fish appears to have dropsy, move them to a quarantine tank and give them a salt bath, per the aquarium salt’s instructions, for 15–30 minutes.

You should also clean their original tank and perform a partial water change.

Potential Tank Mates

You can pair nearly any type of fish with your Siamese algae eaters as long as the fish have the same water parameter needs. However, you should protect your algae eaters from aggressive bottom-dwelling fish, such as the red tail shark.

Below are some of the many excellent tank mates for Siamese algae eaters:

  • Corydoras
  • Guppies
  • Danios
  • Barbs
  • Tetras

Remember, you can also have multiple Siamese algae eaters living in the same tank, given their love for being social.

But regardless of your algae eater’s tank mates, offer them enough hiding spaces where they can get a restful night’s sleep.