Japanese Algae Eating Shrimp Caridina multidentata

One of the most beloved crustaceans among freshwater aquarists is a small and mostly colorless shrimp—the Japanese Algae Eating Shrimp. As its name suggests, this fellow originates from Japan (as well as Taiwan) and has a noted penchant for nibbling upon a wide variety of algae in aquariums. Since they rarely show any interest in bothering live plants, this humble arthropod makes for an ideal part of a planted tank’s clean-up crew, picking all those annoying bits of unwanted algae from leaves that other algae-eating fishes often struggle to reach.

Caridina japonica is a name commonly associated with this shrimp, but a 2006 study of this group concluded that the correct name is actually C. multidentata. Another common name for this species is the Amano Shrimp, after the late Japanese aquascaping innovator Takashi Amano, who first popularized the use of this creature in his magnificent planted tank books. Since then, the availability of this shrimp has skyrocketed, from being virtually unobtainable just a couple decades ago to now being the most ubiquitous crustacean in the aquarium trade, bred in huge numbers on commercial farms.

In the wild, this species occurs in streams and marshes that usually connect to the sea, allowing the microscopic, free-swimming larval stages to float out into brackish or marine waters to complete the life cycle, before eventually returning upstream to live and reproduce in their freshwater home. For this reason, it is rare for juveniles to successfully complete their life cycle in an aquarium without some direct help from the aquarist, which is in sharp contrast to the live-bearing members of Neocaridina (such as Cherry and Yellow Shrimp) which can quickly create large populations in captivity. Males and females are similar in appearance, with the female growing a bit larger and occasionally being seen “in berry” with greenish eggs attached to the underside of the abdomen.

While this shrimp certainly earns its keep, don’t expect C. multidentata to single handedly remove every last speck of algae, particularly from tanks experiencing major algae issues. Some types of nuisance algae, such as cyanobacteria and the dreaded black brush algae are unlikely to be eaten, but most other varieties are. Keep in mind that a hungry shrimp is more effective than one stuffed with uneaten fish food from an overfed aquarium, so, for best effect, keep as many as possible—many (shrimp) hands make light work.