Freshwater Fish

Flying foxfish – Crossocheilus siamensis: the Siamese algae eater

If you’re looking for a freshwater fish to help decrease the amount of algae in your tank, look no further than the Siamese algae eater or flying fox.

These fish have been used as an option for freshwater aquarists with various levels of experience for years, and that isn’t going to stop anytime soon.

This is why:

They are fun and social community fish that can get along with just about any other species you have in your tank.

They are also low maintenance and do not require a great deal of care to thrive. This is a huge draw for many tank owners.

We also think they are pretty fish! Sure, they won’t blow your mind with the color of an African cichlid, but we think they have an understated beauty.

But when it comes down to it, they have a reputation for one specific thing:

Absorb algae.

This combination has made them a very popular fish, which is why it was one of the first fish we wanted to write a care guide for.

In this guide, you will learn everything you need to know about Siamese algae eaters. Understanding how to care for them will help them thrive and allow them to contribute to the rest of your tank as well.


Siamese algae eaters (Crossocheilus siamensis or crossocheilus oblongus) are freshwater dwellers that are members of the carp family of fish species called cyprinids.

This species of tropical fish is found naturally on the mainland of Southeast Asia in places like Thailand, and is a bottom-dweller. They can be found on the Malay Peninsula and in the Mekong and Chao Phraya basins.

Siamese algae eaters prefer their natural habitat in river and stream living environments. They can also often be found in flooded forest regions during the rainy season of this geographic region.


As their descriptive name implies, Siamese algae eaters (or “sae” for short) feed on naturally growing algae found in their native habitats. For this reason alone, these peaceful fish are great at keeping fast-growing algae from taking over an aquarium space over time (they are a lot like the Amano shrimp in this regard).

While many fish experts recommend some algae growth to maintain the proper balance of food and ecosystems within your tank, too much can be detrimental to the fish and other aquatic creatures that live there.

Adding Siamese algae eaters to an aquarium helps control algae growth rates and maintain good aquarium health which is essential to the well-being of every occupant living within the tank. This also prevents cloudy aquarium water (which never looks good).


Siamese algae eaters are long, slender, yellowish-brown fish. This species of fish is identifiable by a bold black stripe that runs the entire length of the body, from nose to tail, with a striking line on each side.

This fringe tends to fade against bottom water features that help the fish camouflage or hide from natural predators in the wild.

The telltale black stripe runs to the tip of the fish’s nearly perfectly transparent tail fin with a mustache some call rostral barbels.

From side to side, the female Siamese algae eater has a somewhat wider spread of her midsection compared to the lean, slender male fish.

Another detail of appearance is that these fish do not have the usual «swim bladder» in most fish. If these fish are not kept in constant motion, they will quickly sink to the bottom of a tank or other aquatic habitat.


Siamese algae eaters can be quite a bit larger than most tropical freshwater fish species you’ll find in various tanks. These bottom-loving fish can grow to about 6 inches (16 cm) and sometimes even a bit longer.

Fish owners should plan on having a tank that is at least 30 gallons in size for the best overall results when caring for this fish. This will give them room to swim comfortably and find places to hide when they need space.


It can be difficult to tell if a fish purchased for an aquarium is actually a Siamese algae eater or a flying fox. The flying fox looks very similar, but fish owners can look for a few differences to ensure they are getting the correct fish.

The flying fox tends to have a light gold stripe that can be seen along the top edge of the telltale black stripe on the sides. A true Siamese algae eater does not have this more distinctive golden edge, although Siamese can have a faded golden tint in certain lights. Another distinctive difference is that the flying fox will have a yellow-orange tint to its fins, and the Siamese’s fins are always light.


Before you commit to caring for Siamese algae eaters, it’s critical to learn how to keep them healthy and what diseases to watch out for.

In general, these fish are wonderful choices for beginning aquarium enthusiasts as they require little care and are not particularly picky about tankmates, food, and other living situations.

One caveat is not to overcrowd the tank with too many Siamese. Although these fish are amazing for their constant tank-cleaning action when feeding on algae, it’s important to remember that any fish, including the Siamese variety, will create bodily waste of their own that can foul your tank.

Below, we dive into the nitty-gritty details about additional tank conditions Siamese fish need to stay healthy and happy. This includes warmer water temperatures, slower moving currents, and lots of cool, shaded areas near the bottom of the aquarium.

With proper diet and care, the lifespan of Siamese algae eaters can be up to 10 years.


Like most species of fish, aquarium owners must feed each species the correct food to maintain health and prolong life. Siamese algae eaters tend to be less picky about the food available and are omnivores. This means that they will eat and collect dead insects, plant matter, and dead fish (among other things).


In their native environments, Siamese algae eaters feed on various forms of algae, phytoplankton, and periphyton. They will also eat dead fish and insects if they find them.


For the best results when caring for Siamese Algae Eaters, you’ll want to recreate their natural freshwater environment as much as possible. This fish likes various tropical algae which will hopefully grow inside an aquarium (since they should mimic a tropical environment).

Most fish experts recommend that these Siamese algae eaters also be fed a dietary mix of fish food that includes some protein and natural plant foods. In the tank, these fish can be fed virtually any commercial or live food.

One precaution in feeding these fish is to not overfeed or overfeed them. When malnourished, Siamese tend to nibble on other plants within the tank that you may not want.

On the other hand, too much protein can make fish less inclined to feed on their preferred menu of algae. This could make the tank more difficult to keep clean, as they will have ruined their appetite!


The Siamese Algae Eater is relatively easy to care for and doesn’t require a lot of fuss or fancy tank conditions to thrive.

In general, plan to go with a minimum size tank of 25 to 30 gallons of water. This will allow them to be active and explore, while also having places to hide.

Keep the pH level of the water between 6.5 and 7.0, which replicates the constant, slightly acidic water conditions these fish find in their usual places in the wild.

Since the Siamese is a tropical fish that lives in freshwater streams and rivers with lower current action, keep the aquarium water temperature at 75°F to 79°F for best results.

The ideal range of water hardness is between 5 and 20 dH.


It is important that the tank includes live plants such as those found in the natural habitat of this species of fish. One tip is to use fast growing plants in case the fish are hungry for a snack and live plants. If they do, the plant can handle it and will soon return to its previous size and height.

The sandy bottom material is also great for keeping this bottom-loving fish safe from scraping rocks or reefs when resting.

Remember to provide plenty of shade and hiding places to keep stress and fatigue levels low while swimming. Small tunnels, swimming holes and hollowed-out logs are perfect additions to the tank of these fish.

Keep a lid over the aquarium to prevent these more active fish from jumping out when cleaning the tank or during feeding times.


The Siamese Algae Eater is known for its calm and peaceful temperament. This characteristic makes these fish an excellent choice for community aquariums that have various types of fish inside.

These constantly moving fish are considered social and get along with many other fish and aquatic creatures normally found in warmer freshwater environments.

There are a few precautions that first time owners should be aware of before introducing this fish to their aquarium. Since Siamese must stay on the move due to the absence of a swimmer’s bladder, these algae eaters need places to hide in the bottom of the tank when they need to rest or want to be alone.

Fish owners can create an ideal habitat for Siamese algae eaters by providing a few cave holes and various plants or objects such as driftwood at the bottom of the aquarium. This gives these active fish a place to get away from others when they need a place to kick back and relax from their busy lifestyles.

The behavior of Siamese algae eaters can be described as active and definitely social. These fish are always on the move and are always looking for algae and other plankton which is usually found on the bottom and walls of the tanks. Due to their active nature, Siamese Algae Eaters are interesting fish to watch compared to their less active counterparts.

Aquarium owners should understand that while these fish are not prone to aggression towards other fish, they can be a stress to other aquarium inhabitants due to their constant movement throughout the tank. This action could stir up another fish’s quiet zone. Adding enough hiding spots helps prevent this problem if you have a community tank.

If a Siamese algae eater appears aggressive, you need to carefully monitor the situation and determine what fish or other creature is causing this normally docile fish to react this way. In rare cases, the fish may need to be kept in a separate tank.

These fish can be somewhat territorial in nature towards their own kind, and it is best to keep a single Siamese or keep 5 or more in a group. This replicates their normal situation in the wild and will prevent a single fish from «claiming» an area of ​​the tank.


Siamese algae eaters are generally bottom-dwelling fish and get along with a wide variety of tank mates. However, choose other bottom-dwelling fish pairs carefully, as the vast majority of bottom-dwellers are somewhat territorial in their normal nature.

Their peaceful nature makes them good companions for a host of freshwater creatures (large and small). Considering fish from the Corydoras family is a tried and true match if you are looking for a specific species to pair them with.

Avoid cichlids and red tail sharks as they are more likely to be territorial and aggressive. A possible exception to this rule is the angelfish.

Some recommended tankmates include:

  • guppies
  • tetras
  • danios
  • spikes
  • Any tame gouramis


It can be difficult to breed Siamese Algae Eaters in a normal aquarium environment. Fish experts simply don’t know much about successful breeding of this species when not in a controlled fish farm environment.

They seem to breed like most fish of their kind, but most fish owners end up relying on fish farms to expand their numbers of Siamese algae eaters. Furthermore, these fish require additional hormones even when reproducing in a farmed environment.

If you’re thinking of breeding Siamese Algae Eaters on your own, don’t get your hopes up. It’s best to keep them happy and healthy if you plan to keep them in your tank.


As you can see these fish are a fantastic and fun addition to almost any freshwater tank and can survive without much attention.

Just take care of their basic needs, and they’ll return the favor by taking care of the algae in your tank!

We hope you now have a better understanding of Siamese Algae Eaters as a species and how to help them thrive. If you have any comments or questions about this fish, you can always contact us and let us know.

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