Genus Atyopsis.
Usually, all shrimps from the genus Atyopsis are referred to by us as the species Atyopsis moluccensis, but most likely here we are dealing with several closely related and difficult-to-distinguish species. Strictly speaking, Atyopsis moluccensis inhabits the Moluccas. However, on numerous islands in the vast region from the Philippines to New Zealand, as well as directly in continental Southeast Asia, very similar shrimps live. In fact, we do not know the exact origin of those shrimps that fate brings to us. It is unclear whether they can all be attributed to a single species, so for now, when talking about these shrimps, it is more correct to limit ourselves only to the generic name – Atyopsis.
— Atyopsis moluccensis — Asian Fan shrimp, Bamboo shrimp, Banana shrimp, Common Fan shrimp, Mountain Rock shrimp, Fan shrimp, Flower shrimp, Rock shrimp, Singapore shrimp, Singapore Filter shrimp, Wood shrimp, Molukkengarnele, Radargarnele.
Inhabits freshwater bodies of Southeast Asia and Malaysia. Males grow up to 7 cm, females up to 8-9 cm. Females are larger and thicker than males. Males differ from females by much more strongly developed front walking legs, which increase significantly with age and are used not for walking, but as hooks holding the animal in the current. Even in the strongest current, the shrimps remain almost motionless, leaving their fans free to catch food. In addition, males use these legs to loosen and stir up the substrate, immediately filtering out everything edible with their fans.
Coloration is highly variable – from brownish to intensely red, with a light sandy-yellow, sometimes white stripe along the back, and changes depending on conditions, recent molting (after molting shrimps become brighter), and diet. They are beautifully colored: sides are sandy-brown, mottled due to numerous longitudinal darker brown stripes, back is bright yellow. But reddish ones can also be found. Some have a greenish-yellow and even red color.
The color of Atyopsis can vary greatly and depends both on the population to which a particular specimen belongs, on dietary features, and even on the shrimp’s mood. They always turn red after molting, then quickly lighten and then change according to their mood, from pale yellow to red-brown. But there is always a yellow or light brown stripe along the back. It is practically impossible to predict in advance what color the shrimps will be in a particular aquarium. However, based on certain signs, in harder water they can be colored more contrastingly and brightly. The color of the substrate and decorations in the aquarium also affects the coloration of the shrimps. Keeping them in a group of at least 4 individuals has a positive effect on the general well-being and coloration of Atyopsis.
In the wild, they eat phytoplankton and zooplankton. They obtain their food using special filtering fans resembling small umbrellas, which give them a completely mind-blowing appearance. Shrimps usually place themselves in plant thickets, sitting on the bottom or on a sloping decoration in the water current, where they filter water with their fans to catch food particles floating by. When there is a group of 6 or more shrimps and free space, they arrange themselves in a neat circle and perform filtration together.
For a happy life, Atyopsis needs a current. Arrange a spot for them somewhere opposite the filter outlet. Stick small sticks directly into the filter stream and attach a few suction cups to the glass, thus creating protrusions on it. Direct the filter outflow toward this glass. All the shrimps will crowd onto the sticks or cling to the suction cups on the glass. As long as there is a current there, you won’t drive them away with a broom. If the current weakens (filter clogged, power cut off), they set off in search of other current sources, for example, bubbles from an air pump. As long as there is a current, they will not wander around your aquarium. They may only try to change position in search of a more comfortable posture for passing water through themselves.
It is recommended to introduce filter-feeding shrimps into an old, silted aquarium with live plants, as the shrimps will be able to find a sufficient amount of food there. They do not eat algae such as filamentous, red, brown, and others, unless small pieces of them float “into their hands”. They have been observed actively eating decaying blue-green algae. In case of a shortage of suspended food in the water, they switch to feeding on detritus, dead plant parts, and other waste.
An important point in keeping Atyopsis, strangely enough, is the presence of a certain amount of suspended particles in the water. In crystal clear water, Atyopsis will inevitably starve. Shrimps must have the opportunity to constantly catch at least something in the water. Clay, for instance, will contribute to the development of the shrimp’s chitinous shell. Shrimps need to be supplemented with food because aquarium water is quite poor in plankton.
As a supplement, any powdered fry food can be used. A small amount of powdered food should be given 2-3 times a day. You can feed them by spraying any dry foods or their mixture, as well as fine frozen bloodworms, into the current. A good way to feed these products is to mix them with water, draw them into a syringe or pipette, and squirt the mixture slowly, drop by drop, right next to the shrimps in the water current. But usually, shrimps get enough nutrition simply from aquarium microorganisms and dry food particles.
In an aquarium, using their fans, these freshwater shrimps strain suspended pieces of dry food, fish excrement, and small pieces of aquatic plants from the water. If all this is not enough to satisfy their hunger, the shrimps begin to sweep the bottom and clean the filter sponge. If you see shrimps sifting detritus on the bottom of the aquarium, this is an indicator that you have improperly prepared feeding stations and need to change the setup so they can feed normally. Although somewhat clumsily, they move quite well along the bottom even on their remaining two pairs of walking legs. Males use their massive hooking claws to plow the bottom like plows and immediately filter the stirred-up turbidity with their fans. Females, on the other hand, are mainly engaged in sweeping the floor.
They are inactive, so we can say that the filter-feeding shrimp is the most boring inhabitant. For this reason, you can keep any peaceful aquatic lifeforms with this shrimp: from newborn guppies to cherry shrimps. Being scavengers and filter-feeders, these creatures have an exceptionally meek disposition. They do not bother any aquarium inhabitants, except perhaps for minor squabbles among themselves over the best position in the filter current.
They need shelters. They often hide in shelters. When necessary, shrimps can hide masterfully. Although this is not a small shrimp, it can camouflage itself so cleverly that it will be difficult to find even in an empty aquarium. But if no one frightens them, they sit importantly on plants or march along the bottom in search of food. They quickly learn the geography of the aquarium where they are housed and subsequently make very clever use of any shelters to escape pursuit. Catching a shrimp is quite difficult. They should only be kept with medium-sized fish.
Keeping Malaysian shrimps presents certain difficulties: they are inhabitants of fast-flowing waters and need well-aerated water. It is advisable not to raise the temperature above 25 degrees, otherwise the shrimp will molt frequently and may quickly die from exhaustion. In addition, these animals are nocturnal, and sometimes you won’t even find them during the day. But by eating algae, they maintain ideal cleanliness in the aquarium. In a strong current, they establish themselves on a rough stone or root where they sit and hold out their fan-like arms.
They are undemanding regarding the chemical composition of the water, but they tolerate high concentrations of nitrogen compounds poorly. That is, the water should ideally be clean with an established biosystem. Regular weekly or bi-weekly water changes are mandatory. The temperature should not drop below 18°C and should not exceed 30°C. Sometimes they are susceptible to fungal diseases. In this case, raising the temperature to 30°C for 2-3 days and active water changes help. Lifespan is 5-8 years. T 23-27°C. pH 6.5-7.8.
Molting in adult Atyopsis occurs irregularly, perhaps once a month or less often, so algae even begin to grow on their shell. Sensing an upcoming molt, Atyopsis stops eating, may simply sit in the current with closed fans, or go look for a secluded spot – like all crustaceans, immediately after molting, shrimps are practically defenseless.
Starting from a size of 3 cm, females are capable of carrying eggs. Immediately after molting, in the presence of males, females try to fertilize the eggs and place them on their pleopods. After two to three weeks, Atyopsis larvae begin to “jump” in the water – tiny dots with a thread-like tail. The larva is quite large, up to 2-2.5 mm. If you turn off the light and shine a flashlight at the glass, they will start swimming towards it. However, truly successful breeding cases are very few. They do not reproduce in freshwater. All small inhabitants of the aquarium, including the Atyopsis themselves, will welcome the new plankton.
The larvae can live in the freshwater of the aquarium for up to a week, after which they die. Just like the Amano shrimp, filter-feeding larvae require brackish water. Practically all filter-feeding shrimps available in stores and markets are wild-caught species harvested from their natural habitats.
Identification: Atyopsis moluccensis.
Atya gabonensis, African fan shrimp, Atya scabra, Rough fan shrimp.
Keeping and care for filter-feeding shrimps. 
