Siamese Algae Eater (Crossocheilus oblongus): Care Guide

Siamese Algae Eaters (Crossocheilus oblongus) are freshwater species of fish that are native to the waters of Southeast Asia. They have gained popularity in the aquarium hobby because of their ability to eat algae. Since they swim fast and work very hard to eat algae in the tank, they are very interesting to observe. Unlike other species that are considered algae eating fish, Siamese Algae Eaters are very agile. This means that they can eat algae in places that other algae eating fish may not be able to reach. This is especially true when they are small.

While they may not be colorful as other tropical fish in the aquarium hobby, they are hardworking fish that are beautiful in their own way. Their body is elongated, with a brown coloration. There is a black horizontal line that goes across their body as well.

This is a great fish to keep, especially if you have an algae problem in your fish tank.

Siamese Algae Eater Facts

  • Siamese Algae Eaters are the best fish at eating algae. With the number of fish species globally, it’s impressive for one species to be considered the best at something.
  • Siamese Algae Eaters are commonly confused for the flying fox and vice versa. Both species come from similar environments, have highly similar bodies and colors, and they even both eat algae. They’re easy to get confused.
  • Despite being a schooling species, Siamese algae eaters are content with being alone, and they don’t seem to get lonely. But if they are kept in a smaller group, usually around three or four, they can become a bit territorial and aggressive towards other males in their species.
Siamese Algae Eater
Siamese Algae Eater (Crossocheilus oblongus)

Siamese Algae Eater Care

Siamese algae eaters are fantastic fish for beginners. They are relatively easy to care for, aren’t too picky about potential tank mates, and can thrive in a wide variety of tank setups.  The biggest concern with Siamese algae eaters is overpopulating their tanks. You may think that the more Siamese algae eaters you have, the cleaner your tank would be. But, that honestly is not the case; it’s actually the opposite. The more fish you have, the more bodily waste will be produced. That waste will quickly begin to pollute your tank, so you don’t want to overcrowd it, especially with Siamese algae eaters.

Temperature for Siamese Algae Eaters

Siamese Algae Eaters are native to the tropical freshwaters of Southeast Asia; this means they prefer warmer water than other species of freshwater fish. They prefer their water to be between the temperatures of 75 degrees Fahrenheit to 79 degrees Fahrenheit or 24 to 26 degrees Celsius. This narrow temperature range means that you need to be extra vigilant about changing water conditions or problems with your aquarium heater. It also decreases the number of potential tank mates, but you can easily find species that would be glad to share a tank with Siamese algae eaters with a bit of research.

Water pH for Siamese Algae Eaters

The waters that the Siamese algae eater are native to are somewhat acidic rivers in Asia. This means their preferred pH level when kept in captivity is also somewhat acidic. Siamese algae eaters prefer a pH level between 6.5 -7.0, but they can survive in a broader range of 6.0 – 8.0.  That wide range allows Siamese algae eaters to become tank mates with an extensive range of fish. They’re a very timid species that tend to stay at the bottom of tanks which means they won’t interact with most other species.

Siamese Algae Eater Size

Siamese algae eaters are bottom-dwellers which means they won’t often leave the bottom of the tank to interact with other species. This feature is helpful because their larger size could intimidate some other species. Siamese algae eaters can grow up to six inches in length, making them larger than most other common freshwater species traditionally found in aquariums. Some Siamese algae eaters have been known to grow larger than six inches. But for them to reach six inches or larger, your Siamese algae eater needs to be adequately cared for. Proper care includes the right pH balance, temperature level, and tank setup. Their larger size also indicates that they need a larger tank than some people are comfortable owning and caring for.

Tank Size for Siamese Algae Eaters

Siamese algae eaters are larger fish species than most other aquarium fish; this means they need a bigger tank than most. Most professionals would recommend a 25 – 30 gallon tank for Siamese algae eaters. 25 – 30 gallons gives them adequate room to explore and dart around the tank and provides plenty of space to place decorations and other tank objects for them to hide in or around. Siamese algae fish love to have things to hide in, such as caves or hollowed-out logs. They also love plants to hide among and plenty of shade. They’ve also been known to jump, so a tank lid is recommended.

Siamese Algae Eater Food & Diet

Siamese algae eater’s name gives their food and diet preferences away. They like to eat algae, simple as that. Siamese algae eaters will snack on algae in the wild, obviously, along with periphyton and phytoplankton. They’ve also been known to feast on dead fish and insects. When they’re kept in captivity, you want to emulate this varied diet. That means you should be sure to grow several types of algae in your tank for your Siamese algae eaters to snack on. It is recommended to feed them a diet of fish food, such as flakes or pellets that contain protein. It is imperative to not under or over-feed them. Overfeeding them other foods means they won’t need to eat algae; your tank could quickly become overrun if they don’t eat algae. On the other hand, underfeeding them is also an issue; it means they’re more likely to nibble on any plants in your tank.

Do Siamese Algae Eaters Eat Hair Algae?

As their name implies, Siamese algae eaters will eat many different varieties of algae, including hair algae.  Most seasoned aquarists can tell you just how annoying hair algae is. Once it starts to grow in your tank, it is pretty hard to get rid of. That’s where Siamese algae eaters come in. The slender fish will dart around the tank and happily eat all the hair algae. So, if you’re having a problem with hair algae, consider purchasing a few Siamese algae eaters. That is as long as your tank allows them, of course.

Do Siamese Algae Eaters Eat Brown algae?

Siamese algae eaters are a highly effective way to combat most algae types because they eat most algae—brown algae are one of the types they like to eat. Siamese algae are very helpful at keeping your tank algae free. They’re also a very peaceful species and will most likely spend their time hiding on the bottom of your tank or in any tank decorations. This persists until they decide they’re hungry, at which point they’ll likely begin looking for algae or anything else to snack on.

Siamese Algae Eaters Lifespan

Siamese algae eaters can live up to 10 years on average, and this lifespan is longer than most aquarium fish. But it is important to remember that their lifespan is directly related to their care. If you do not give your Siamese algae eaters proper care, they will never reach that impressive life span. Be sure to monitor their tank for any potential fluctuations in pH level or temperature; catching those changes early mean you can actively work to ensure they return to normal. It is also imperative to avoid any species that will come into conflict with your Siamese algae eaters.

Tank Setup for Siamese Algae Eaters

Siamese algae eaters need a well-planted tank to survive. The plants help with fulfillment as they’ll dart among them, enjoying themselves. They will also produce oxygen, which is essential to the Siamese algae eater’s survival. A sandy substrate is vital because they will spend most of their time on the bottom of the tank, and anything more coarse could hurt. Finally, any tank that includes a Siamese algae eater should have algae and tank decorations. The algae are for them to eat and the decorations for them to hide in or among. Siamese algae eaters like long, hollow decorations as they can swim through them.

Breeding Siamese Algae Eaters

Siamese algae eaters are a notoriously difficult fish to breed in an aquarium. Experts do not know much about their breeding patterns, and all they know is that Siamese algae eaters tend to reproduce like most other fish species. If you want to add more Siamese algae eaters to your tank, it is not recommended to try breeding; you should purchase them. There is some luck breeding them in dedicated fish farms, but they need additional hormones to reproduce successfully.  You should focus on keeping your Siamese algae eaters happy and healthy instead of trying to breed them.

Diseases Common to Siamese Algae Eaters

As with most other aquarium fish species, Siamese algae eaters can quickly become afflicted by a disease known as Ich. Ich is easily identifiable by the appearance of white spots on the body of the affected fish. Ich is quite contagious, so any affected fish should be quarantined as soon as it’s noticed. Thankfully, Ich usually responds very well to medications, and the fish will heal quickly once the medication is administered. If your tank is well monitored and kept in your inhabitants’ preferred ranges, most diseases and illnesses can be avoided. Good food is also essential; lower quality food is more likely to cause constipation in your fish, leading to digestive issues.

Tank Mates for Siamese Algae Eaters

Finding suitable tank mates for Siamese algae eaters isn’t a challenging task. They’re peaceful bottom-dwelling fish, and their temperament and tank location make them compatible with most other peaceful freshwater fish species. The most important thing to consider is the tank needs of the other species. Siamese algae eaters don’t have the most demanding tank and water conditions, meaning they’ll be able to share a tank with several different species.

Are Siamese Algae Eaters Aggressive?

Siamese algae eaters usually are very peaceful species. They’ll likely be too busy in your tank to worry about being aggressive towards other species. They’re usually very busy darting around the tank, looking for any algae to eat. Siamese algae eaters are one of the most peaceful species you could add to your tank. There is one scenario where they are known to be aggressive, however. Siamese algae eaters are a schooling species, which means they prefer to be kept in a group of their own species. If kept in a small group, males may become territorial and aggressive towards one another.

Compatible Tank Mates for Siamese Algae Eaters

It isn’t difficult to find species compatible with Siamese algae eaters. They are very peaceful fish, more worried about finding algae to eat than they are other fish. Siamese algae eaters are more likely to get aggressive with their species than with other species of fish. The biggest concern when weighing options for tank mates is that the potential tank mates have to have a similar temperament. They also need to have overlapping temperature preferences and pH needs, as well as other tank requirements. Some species compatible with Siamese algae eaters are guppies and more Siamese algae eaters.

  • Siamese Algae Eaters: The species most compatible with Siamese algae eaters are Siamese algae eaters. They’re schooling fish, meaning they should be kept with others of the same species, but Siamese algae eaters are perfectly content to be alone, unlike most other schooling species. They don’t get stressed or sad when alone, but they also love to be in a group. When they’re kept in a group, you have to make sure the group isn’t too small because when their school is too small, males will become territorial and aggressive.
  • Guppies: Guppies are extremely popular, and I assume at least a few of you reading this article own some guppies. So you’re likely wondering if you can put Siamese algae eaters in the same tank as guppies. The answer is yes. Guppies and Siamese algae eaters are primarily passive, so they shouldn’t conflict with one another. Just be sure you have a tank large enough to accommodate the needs of the Siamese algae eater.

Incompatible Tank Mates for Siamese Algae Eaters

Due to Siamese algae eaters’ peaceful nature, they should never be kept in a tank with aggressive species. The more aggressive species will not like the Siamese algae eater’s quick and mobile nature when they’re looking for food. You should also avoid pairing Siamese algae eaters with other bottom dwellers. Most bottom-dwelling fish can be very territorial, and they won’t like the Siamese algae eater staying at the bottom of the tank. Some species incompatible with Siamese algae eaters are red tail sharks and tiger barbs.

  • Red Tail Shark: Despite their name, red tail sharks are not actually a species of shark, and they are, in fact, a species of carp. They can get quite aggressive and territorial; this is not a good match for Siamese algae eaters. While the red tail shark may not physically attack the Siamese algae eater, they will chase it to the point of exhaustion. That exhaustion and stress are not good for the lifespan of your Siamese algae eater.
  • Tiger Barb: Tiger barbs usually are considered a bit of a nuisance to other fish. They’re not over-aggressive with other fish, but they can be annoying. Tiger barbs are likely to nip at the fins of your Siamese algae eaters; because of this, they likely won’t be able to coexist happily in the tank. Fin nipping may seem a bit minor to some, but it can lead to much bigger problems. It will stress out the fish and will likely lead to infections and illnesses in the fins that were nipped.

Siamese Algae Eater and Betta Fish

Siamese algae eaters are very peaceful; Siamese fighting fish, on the other hand, are not. But, betta only tends to be aggressive towards other bettas. With that in mind, betta fish, also known as Siamese fighting fish, should coexist in a tank with Siamese algae eaters. In a large tank, the betta fish and the Siamese algae eater will rarely come into contact with one another as they don’t tend to be around the same parts of the tank.

Siamese Algae Eater and Corydoras

Corydoras or Cory catfish are bottom-dwellers like the Siamese algae eater, and neither species are territorial or aggressive. This means that the two species of bottom dwellers will get along very well together despite sharing the same part of the tank. You need to be sure that your tank is large enough to accommodate your two species of bottom dwellers. Also, be sure that your tank is well planted sufficient to keep them both happy and that the substrate is soft enough not to irritate them.

Siamese Algae Eater and Goldfish

Goldfish and Siamese algae eaters likely aren’t very compatible with each other. They don’t overlap temperature-wise. Goldfish are easy to take care of and can exist in tanks at room temperature without heaters. Siamese algae eaters are more tropical, prefer warmer waters, and likely need a heater to achieve those conditions. That’s unfortunate because, besides that, Siamese algae eaters and goldfish would probably be compatible. They have very similar temperaments and likely wouldn’t come into conflict with each other.

Siamese Algae Eater and Gourami

Gourami, specifically dwarf gourami, make great tank mates for a Siamese algae eater. Both of these species are very peaceful; neither of them want to start trouble with any other fish. Their temperature needs are also highly similar, that is because they are both tropical freshwater fish. That’s also why their pH requirements are also nearly identical. As long as your tank is large enough to accommodate both the Siamese algae eater and any species of gourami, you shouldn’t have a single issue. They are compatible and should get along swimmingly.

Siamese Algae Eater and Cichlids

Most, if not all, species of cichlids can be very aggressive, and that temperament makes them a wrong choice to have in a tank with the ordinarily peaceful Siamese algae eater. That means that cichlids and Siamese Algae eaters are not compatible. When it comes to taking care of algae in a tank that features cichlids, you’ll likely have to do it on your own. This is because the cichlids are likely to get aggressive towards whatever species you try to use to eat the algae.

Siamese Algae Eater and Amano Shrimp

Amano shrimp and Siamese algae eaters both feed on algae. In most cases, when fish, or any animal for that matter, compete for the same food source, they are likely to be aggressive towards each other. This is not the case with Amano shrimp and Siamese algae eaters. Despite them sharing the same food source, Amano shrimp and Siamese algae eaters are compatible within a tank. The only thing to keep in mind is that you’ll likely have to supplement their diet with additional food. But keep in mind not to overfeed them as they will be more effective algae eaters if they aren’t overfed.

Siamese Algae Eater and Neon Tetra

Neon tetras are gorgeous, so most people would likely want to include them in their community tank. As such, the question of compatibility arises. Siamese algae eaters and neon tetras should get along very well together. Both species are peaceful and don’t tend to get aggressive towards other species, and you should be able to keep them together in the same tank without worry.

Where can I find Siamese Algae Eaters for Sale?

Siamese algae eaters are quickly becoming more popular, meaning more stores have started to carry them in stock. You can find Siamese algae eaters for sale at most aquarium specialty stores and likely in some pet stores. They usually sell for around $5 each, but keep in mind that you should purchase more than once since they are a schooling species.

Siamese Algae Eater vs Flying Fox Fish

Siamese Algae Eater (Crossocheilus oblongus) and Flying Fox Fish (Epalzeorhynchos kalopterus) are incredibly similar, but there are some differences. They both eat algae, although the Siamese algae eater is more adept at it. The two species have very similar body shapes and colorings. They’re also native to the same waters in Southeast Asia. Siamese algae eaters and the flying fox have slightly different mouths. Siamese algae eaters have flaps near their mouths that look almost like whiskers. Their coloring is also somewhat different. The flying fox’s body is usually one clean color, whereas the Siamese algae eater’s body is several different shades with dark outlines. Both the flying fox and the Siamese algae eater have a black stripe along their bodies. The black stripe on the flying fox is completely straight and uniform, the black stripe on the Siamese algae eater, is not as straight. It almost makes a zig-zag pattern with the color bleeding into the adjacent scales.

Siamese Algae Eater vs Chinese Algae Eater

Siamese Algae Eater (Crossocheilus oblongus) and Chinese Algae Eater (Gyrinocheilus aymonieri) are both algae eaters, but they aren’t the same fish. Chinese algae eaters are much more aggressive and grow much larger than their Siamese counterparts. Chinese algae eaters tend to be a yellow color and have a very pronounced suckermouth. Neither of which can be said for the Siamese algae eater.

Siamese Algae Eater vs Otocinclus Catfish

Siamese Algae Eater (Crossocheilus oblongus) and Otocinclus Catfish (Otocinclus affinis) are both algae eating fish, and they are both very popular in the aquarium hobby. Since both are great at eating algae, you may wonder which one is better for your tank setup. Depending on the size of your tank, the otocinclus catfish may be the better choice. They only grow to be around 2 inches in length, a third of the Siamese algae eater’s 6 inches in length. Otocinclus are strictly herbivores; Siamese algae eaters are omnivores meaning they need a more rounded diet. Siamese algae eaters and Otocinclus catfish would make pretty great tank mates. They have very similar tank needs, share a similar diet, and even have nearly the same temperament.


The Siamese algae eater is a species of fish that mainly does one thing, which may not seem appealing to some. But that one thing they do, eating algae, they do better than any other species. If you have an algae problem in your tank, you should strongly consider adding a few Siamese algae eaters. They will quickly take care of the problem and make sure it doesn’t arise again. The Siamese algae eater is good at their job, simple as that.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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