Siamese algae eater - Crossocheilus siamensis
Pilgrim Fish
The Siamese algae eater primarily originates from the basins of the Malay Peninsula, Thailand, and the Chao Phraya and Mekong rivers. The general term used by villagers living in the Mun River basin, which flows into the Mekong, for fish that migrate upstream during the dry season is "third month fish" or "pilgrim fish".
In Northeastern Thailand and Laos, the lunar calendar is still used to determine the timing of important dates and religious ceremonies. Coincidentally, the upstream migration period of the Siamese algae eater corresponds to the third month of the lunar calendar, hence these fish are called "third month fish." During this time, locals go to the pagoda for worship services, and since it seemed that these migrating fish had a similar habit, they are called "Pilgrim Fish."
Habitat and Distribution
Crossocheilus siamensis is very adept at moving in the current, clinging to surfaces even in very strong currents, where it consumes algae from the surface of rocks and from plant leaves. This implies that they can also effectively control algae growth in artificial aquarium environments.
Physical Description
The Siamese algae eater has a slender, elongated body that can grow up to about 15 cm in length. They are usually brownish or grayish with a black horizontal stripe running from the snout to the tail. This coloring is effective for blending in with the surroundings and avoiding predators.
Diet and Algae Control with Crossocheilus siamensis?
The diet of Crossocheilus siamensis primarily consists of various types of algae and small microorganisms. In aquarium settings, they are particularly valued for their ability to consume not only green algae but also more resistant types of red, black, and brown algae, which many other fish avoid. However, as Diana Walstad points out in her book Ecology of the Planted Aquarium, long-term dependence on fish or other living organisms may not be sustainable, because algae eaters will target the algae they prefer to consume. If, however, the tank is unbalanced, it is only a matter of time before other less palatable algae appear. For example, cyanobacteria are not algae, so no aquarium fish will eat them; conversely, only the Black-striped barb will eat black brush algae.
Behavior and Tolerance
The Siamese algae eater is a peaceful fish, making it a suitable member of community aquariums. They are more effective in groups. However, when they mature, they can become territorial towards each other. For this reason, it is important to provide adequate space and give them hiding places in the aquarium to reduce stress and aggression.
Breeding
Breeding Siamese algae eater / Crossocheilus siamensis in captivity is very challenging and they are therefore part of imports. Their breeding habits in the wild are not well documented. One reason might be that their migration and most likely also their breeding occur when the water is cloudy and less accessible. As local fishermen confirm:
- "When the river turns red after the rains begin, all the fish move upstream."
- "Fish come into the Mun River when the water rises and the flow of the river gets faster and the water becomes cloudy."
- "In order for upstream migration to start, the rains must fall and the water must get cloudy."
Conservation and Importance
Although the Siamese algae eater is not currently listed as an endangered species. The environment of Crossocheilus siamensis is threatened by factors such as pollution, dam construction, and habitat destruction, which negatively affects the population of Black-striped barb.
Keeping Siamese algae eater in Aquariums
For aquarists interested in keeping Siamese algae eater, it is important to mimic their natural environment as closely as possible. This includes providing an aquarium with ample space, good water flow, plenty of hiding spots among plants and rocks, enough oxygen, and various surfaces for algae growth. The Siamese algae eater is a peaceful species that can coexist with a wide range of other peaceful fish in the tank. It thrives best in groups. It is more active and effective in removing algae when kept with others of its kind. Regular maintenance and water quality checks are crucial for maintaining the health of the Siamese algae eater.
Source:
Algae Eating Cyprinids from Thailand and Neighboring Areas, by Neil Frank and Liisa Sarakontu (https://www.aquatic-gardeners.org/Articles/cyprinid/)
A River, Its Fish and Its People: Local Knowledge of the Natural Environment at the Mouth of the Mun River, May 2004 (The original title of this report in Thai is, Mae Mun, kan klap ma khong khon haa plaa:bot sarup lae khwam ru ruang pla khong khon Pak Mun, kan wicai thai ban.)
Walstad, Diana. Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise for the Home Aquarist. Echinodorus Publishing, 2023.
