Siamese Algae Eaters: Size, Care and More

Siamese Algae Eater (lat. Crossocheilus oblongus) is a fish of the Cyprinidae family. It is often called SAE, fish which is an abbreviation from its full name. It is used in aquarium husbandry as a natural way of fighting unwanted algae. It is considered the most efficient of all known algae eaters. This fish is the only known fish genus that can eat coarse algae, and it will be a good helper for you to deal with black beard algae (BBA) in a tank. The fish is peaceful, not very large, and it is a true tank cleaner. It eats algae in a tank, and this task is quite challenging since not every fish can do it.

Habitat in the wild

The Siamese algae eater (Crossocheilus siamensis) belongs to the family Cyprinidae. This family includes a wide variety of freshwater fish commonly known as carps, barbs, danios, rasboras, and other related species. As a member of the Cyprinidae family, Siamese algae eaters share characteristics typical of this group, such as a streamlined body shape, a single dorsal fin, and usually lack barbels (whisker-like sensory organs around the mouth).

Earlier it was considered to belong to the Epalzeorhynchus genus according to scientific classification. Now, it belongs to the Crossocheilus genus, but the fish itself is important, not its name.

The Siamese algae eater (Crossocheilus siamensis) is native to freshwater rivers and streams in Southeast Asia, particularly in Thailand, Malaysia, and other nearby countries. Their natural habitat consists of fast-flowing, clear waters with rocky or gravel substrates, and they are often found in areas with dense vegetation along the banks.

In their natural environment, Siamese algae eaters are accustomed to moderate to strong water currents, and they prefer well-oxygenated water. These fish are commonly found in regions with abundant algae growth, which is their primary source of food. Their diet includes various types of algae, plant matter, and small invertebrates.

Crossocheilus oblongus lives in fast streams and rivers with a rocky bottom that consists of fieldstones, gravel, and sand with many snags or tree roots. Low water level and transparency create favorable conditions for blusterous algae growth, and the fish feeds on them.



In the wild, siamese algae eater may grow up to 16 centimeters (6.3 in) large, while it is usually smaller in a tank – up to 12 cm (5 inches).


The Siamese algae eater typically has a lifespan of about 5 to 7 years in captivity. However, it’s important to note that individual lifespans can vary depending on various factors such as the quality of care, water conditions, diet, and genetics.

Keep in mind that fish lifespan estimates are based on general averages, and some individuals may live longer, while others might have shorter lifespans. Monitoring the health and behavior of your Siamese algae eaters can help you identify any potential issues and take appropriate actions to promote their longevity.


It has an elongated silvery-colored body with a dark stripe. The fins are almost transparent without any visible color or tint. The black stripe starts from the nose tip and goes till the tail fin end. When the SAE fish is stressed, the stripe becomes light-gray.

The tripe is not perfectly straight, and it has visible notches. Above the black stripe, if looking at some specific angle, you may see one brighter colored stripe. There is a pair of barbs on the fish underlip. Its jaws allow SAE fish to scrape algae fouling from plants, decorations, and tank equipment.

Scientific NameCrossocheilus siamensis
Common NameSiamese Algae Eater, SAE fish
OriginSoutheast Asia (Thailand, Malaysia, etc.)
SizeUp to 6 inches (15 cm) in length
Lifespan5 to 10 years in captivity
TemperamentGenerally peaceful and sociable
Water Temperature74°F to 79°F (23°C to 26°C)
pH Range6.5 to 7.5
Water HardnessModerately soft to moderately hard
Tank SizeMinimum 20 gallons (75 liters) for a small group
DietHerbivorous – Algae, plant matter, and small invertebrates
HabitatFreshwater rivers and streams with dense vegetation
Preferred Water FlowModerate to strong water currents
Suitable TankmatesPeaceful community fish with similar water requirements
BehaviorActive and enjoys exploring the environment
Algae ControlEffective algae grazers, but supplemental diet needed
Special ConsiderationsAvoid aggressive or territorial tankmates

True Siamese algae eater vs. siamese flying fox fish

Except for Siamese algae eater, you may also encounter another fish – Flying Fox (Epalzeorhynchos kalopterus) on sale. The thing is that these two fishes are very much alike, and quite often, one is taken for another.

And now you are going to ask: so what’s the big difference? The difference is that flying fox deals with tank algae not as good as SAE fish, and what is more important, unlike SAE fish, this fish demonstrates aggressiveness towards its tank mates. Therefore, it is less welcome in community tanks.

Once you know what you should pay attention to, you’ll easily tell between these two fishes.

The main feature of the fish is a black stripe along its body. True Siamese algae eater has denticular shaped black stripe that starts from the fish mouth and ends on the edge of its tail fin. As for the flying fox, its black stripe ends on its body where the tail fin starts (the fin is transparent). All upper side of the fish body has a brown tint, and each scale has dark edges, which makes its body pattern look reticulate.

Siamese algae eater has a pair of thin forward barbels, but they may rest on the fish cheeks when it swims or relaxes. Adult flying fox species have red coloring around their mouth.

A true SAE fish has three support points when it lies on a tank bottom – these are its tail and abdominal fins at that the fish doesn’t touch the substrate with its pectoral fins.

Siamese algae eater vs. algae

Quite often, algae turn into a real problem in a tank. Many approaches are used to fight them, one of which is biological – using fishes eating the unwanted vegetation. SAE fish is very efficient in cleaning the tank from inferior plants.

This is the only fish kind kept in tanks capable of stopping algae attack at the very beginning. Its mouth is made to capture young algae. Those that are at later stages of development don’t interest the fish.

The same is true about green fouling on tank walls. SAE fish can’t deal with it, but many catfishes such as bristlenose pleco or sailfin pleco can.

To maintain a small tank in ideal condition, two SAE fish are enough. At that, young species deal quite well with algae while adults prefer more nutritious food, and they are less efficient against algae.

Difficulties in keeping

The fish is a peaceful, active, and not demanding one. Besides, it is one of the few who can fight algae in a tank. The main siamese algae eater peculiarity is that it can eat black beard algae, unlike other fishes, which don’t even come close to this kind of algae.

However, to make siamese algae eater eat BBA, the fish should be half-starved, which means you should overfeed it. Juveniles eat black beard algae more eagerly, while adult species prefer live or artificial food.

Keeping in a tank

SAE fish likes free-floating in the wild and behaves timidly and fearfully if kept separately from other fishes or small groups. The fish feels more comfortable in a group of 5-6 or more species (depending on the tank volume). In this case, you’ll be rewarded with a more natural appearance and behavior of the fish, plus the chance to observe how fish interact in a group.

It is active and spry, but it likes to have some rest from time to time. It tends to choose several tank plants with wide leaves to rest on them. The juveniles may use narrow leaves of tank plants for the same purpose. If there are no proper plants in the tank, they rest on the tank bottom.

Tank size

Siamese algae eater is rather not picky. Due to its relatively large size, a couple of adult SAE species requires a tank not less than 40 gallons (approximately 150 liters) capacity. They are extremely lively and juice up the tank scenery.

Having a larger tank is always beneficial as it allows for more swimming space and provides opportunities to create a diverse and stimulating environment with rocks, driftwood, and live plants. Siamese algae eaters are active fish, and a spacious tank will help them exhibit their natural behaviors more comfortably.

Keeping them in a larger tank also aids in maintaining stable water parameters and reduces the likelihood of aggression among tankmates. Additionally, a larger volume of water allows for better dilution of waste products, promoting a healthier and more stable aquarium ecosystem.

Water parameters

Here are the recommended water parameters for these fish:

  1. Water Temperature: 74°F to 79°F (23°C to 26°C). Siamese algae eaters prefer tropical temperatures within this range.
  2. pH Level: 6.5 to 7.5. Siamese algae eater can live at a wide range of water parameters, but it prefers neutral or a bit acidic water.
  3. Water Hardness: Moderately soft to moderately hard. Aim for a general hardness (GH) level between 5 to 12 dGH and a carbonate hardness (KH) level between 4 to 8 dKH.
  4. Ammonia, Nitrite, and Nitrate: Keep ammonia and nitrite levels at 0 ppm, as these are toxic to fish. Nitrate levels should be kept below 20 ppm. Regular water changes and proper filtration help to maintain low nitrate levels.
  5. Filtration and Oxygenation: Siamese algae eaters prefer well-oxygenated water with moderate water flow. Proper filtration is essential to remove waste and maintain good water quality.

It’s essential to regularly test the water parameters using reliable test kits to monitor the aquarium’s conditions. Frequent water changes (around 20% to 25% of the total water volume) every 1-2 weeks will help maintain stable water parameters and promote the overall health of the fish. Don’t forget that tap water is often a source of such toxic components for the fish as chlorine and high-density metals. Thus during every water renewal, use water conditioned that in a moment makes the water suitable for its dwellers. It removes toxic substances and enriches water with vitamins.

Remember that sudden and drastic changes in water parameters can stress or harm the fish, so try to keep the water conditions consistent. When introducing new fish to the aquarium, it’s advisable to acclimate them slowly to the existing water parameters to minimize stress.

Tank setup: decorations and plants

It is desirable to have not a high but a long thickly-planted tank with noticeable water flow. Since SAE fish typical biotope is a well-lighted fast-flowing stream or river, the tank water should be crystal clear and rich in oxygen. This means that if there are some areas with backwater and poor oxygen content in the tank SAE fish won’t feel comfortable there.

They are active; however, their air bladder’s construction doesn’t let them stay in the water all the time. Siamese algae eater can be often seen lying on the substrate or large leaves of tank plants. Thus, it is recommended to organize the tank, so it has bunches of live plants and enough space to swim.

The fish can easily jump out from the tank, so it is required to cover it with a glass-cover slip or put some fluctuant on the water surface.

You can use small-sized gravels as a tank bottom substrate, and put some snags or stones into the tank is also a good idea. Lighting doesn’t play an important role. Both bright and scattered light is good for the fish. For this reason, when selecting lamps for the tank, you should keep in mind the tank plants requirements.


Since the wild siamese algae eater inhabits ponds with circulating water, they prefer clean water rich in oxygen. To swim around the tank, SAE fish needs water flow since it reminds the fish of its natural habitat. If there is no flow in the tank, you can create it using a powerful canister filter. Don’t forget about daily water renews (about 30% of the tank capacity).


Siamese algae eaters (Crossocheilus siamensis) are primarily herbivorous fish that feed on various types of algae and plant matter in their natural habitat. In the aquarium, their diet should consist of a combination of algae-based foods and supplementary plant-based or protein-rich foods. In a tank, it scrapes algae from tank plants, decorations, and equipment. Providing a well-balanced diet ensures their nutritional needs are met and promotes good health and coloration.

When in a tank, the siamese algae eater eats all types of live, frozen, and dry specialized food. SAE fish should have a diversified diet with a large amount of plant food in it. If the plant component content in the fish diet is not enough, it may start eating tank plants, especially moss types. Juveniles eat algae more eagerly, while adult species prefer protein food most.

Here are some suitable foods for Siamese algae eaters:

  1. Algae Wafers/Pellets: High-quality algae wafers or pellets designed specifically for herbivorous fish are readily available in the market. These sinking foods contain essential nutrients and serve as the primary source of sustenance for Siamese algae eaters.
  2. Algae: Allow some algae to grow naturally in the aquarium for them to graze on. You can also attach algae-covered rocks or decorations to provide additional grazing spots.
  3. Blanched Vegetables: Offer blanched vegetables like zucchini, cucumber, spinach, or lettuce. These should be softened by briefly boiling or steaming before offering them to the fish.
  4. Frozen or Live Foods: Siamese algae eaters can also accept some frozen or live foods as part of their diet. Daphnia, brine shrimp, and bloodworms can be occasional treats.

Offer a variety of foods to ensure they receive a balanced diet. Feed them in small portions a couple of times a day, as overfeeding can lead to water quality problems and obesity. If there are other fish in the aquarium, make sure the Siamese algae eaters get their share of the food, as they can be outcompeted by more aggressive eaters.

Tank mates

SAE fish is a good-tempered fish, and it can be a decent tank mate for most unaggressive fishes, though it’s better not to keep it with long-finned ones since siamese algae eater may nip their fins.

As for unwelcome siamese algae eater tank mates, this is a rainbow shark. The thing is that both species are related and territory-dependent ones. They inevitably will have fights, and it’ll end up with the death of one of them. Males show territory dependence towards each other. Therefore it’s better not to keep a lot of males in a small tank.

Since the fish is very active, it’ll be a troublesome tank mate for cichlids that guard their territory during the spawning period, and SAE fish will disturb them all the time by swimming around.

In the wild, siamese algae eaters practice free floating, and they may be quite timid and hesitant when kept separately or in a small group. The optimal group size is 5-6 species or more (depending on the tank capacity). You’ll be rewarded by seeing more natural fish appearances plus interesting behavior and interaction between them.

Gender differences: male vs female

Determining the sex of Siamese algae eaters can be challenging, especially when they are young or not in breeding condition. These fish do not exhibit significant external sexual dimorphism, which means there are no obvious physical differences between males and females.

In some cases, mature female Siamese algae eaters may appear slightly larger and rounder when carrying eggs, but this distinction might not be apparent unless you have experience or observe them closely during breeding behavior.

Due to the difficulty in visually identifying their sex, most Siamese algae eaters are sold as unsexed individuals in the aquarium trade. If you are looking to have a male and female pair for breeding purposes, it is best to acquire a group of these fish and let them pair naturally if they decide to breed.

Keep in mind that Siamese algae eaters are more commonly kept for their algae-eating behavior and not primarily for breeding. When kept in a group, they can still exhibit fascinating schooling behaviors and help keep the aquarium clean by grazing on algae and detritus.


There is no reliable information about siamese algae eater breeding successfully in a home aquarium (without hormonal agents’ support). The species you see on sale are either bred in fish farms or were caught in the wild.