Amano shrimp

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Typically wild-caught; acclimate slowly.

Feeding

Aggressive grazer of soft green algae, hair algae, and young black beard algae, often clearing visible coverage from a tank within a few days. Algae alone is not enough food, though, so a clean tank should be topped up with algae wafers, sinking shrimp pellets, blanched vegetables, and occasional protein foods. Amanos are bolder than cherry shrimp and often grab a piece of food and dart off with it, sometimes stealing from smaller shrimp.

Compatibility

• Compatible with the typical peaceful community. Large enough that most fish ignore them, in contrast to neocaridina dwarf shrimp
• Healthy plants are not at risk. Soft, dying leaves get picked at, which is useful
• Coexists with cherry shrimp without aggression, though amanos will out-hustle them at feeding time and take more than their share
• Keep them away from large cichlids, puffers, and anything that targets invertebrates as food
• Copper kills shrimp. Check the active ingredients on any medication or plant fertilizer before dosing a tank that contains them

Origin and habitat

Originally from East Asia, with populations across Japan (most common in the southwest, where the species is called yamato shrimp), Taiwan, and Korea, plus records from parts of coastal China. The natural habitat is clear, fast-running freshwater streams with rocky beds and plenty of vegetation. Stimpson described the species as Caridina multidentata in 1860, but a later name, C. japonica (De Man, 1892), stuck for decades until Cai and Shokita revisited the taxonomy in 2006 and restored the older name; both still circulate in the hobby. The species epithet, multidentata, refers to the high tooth count on the rostrum. The life history is amphidromous: adults live in fresh water, females release planktonic larvae that drift downstream into brackish or coastal water to develop, and juveniles eventually migrate back up. That cycle is why standard freshwater aquaria do not produce next-generation shrimp. The aquarium aquascaper Takashi Amano started using the species for algae control in his Nature Aquarium work from the 1980s onward, and the common name attached itself to the shrimp from there. Adults run about 4 to 5 cm, females are a bit larger, and a berried female carries on the order of hundreds to a few thousand very small eggs (roughly 0.3 to 0.5 mm). The body is greyish to olive and translucent, broken by a row of reddish-brown markings along each flank; in males those marks are more like dots, and in the larger females they elongate into dashes. A pale stripe runs along the top of the body. IUCN Least Concern.

Breeding

Not viable in standard freshwater. Females carry eggs readily, but the offspring hatch as planktonic larvae that need brackish to near-saltwater conditions to survive, and the larvae cycle through roughly nine stages over four to six weeks before they look anything like adults. Anyone who wants to attempt it has to move a berried female to a separate brackish setup before the larvae hatch, rear them in well-lit, algae-rich water (the lighting is to support the algae and phytoplankton the larvae feed on), then slowly bring the survivors back to fresh water. Loss rates are heavy even with practice, which is why almost every amano in the trade is wild-caught.

Common problems

Climbing out of the tank is probably the single largest source of accidental loss. Amanos can pull themselves up airline tubing, heater cords, filter intakes, or any rough vertical surface, so a cover with no gaps is necessary. At feeding time they tend to muscle smaller shrimp off food and run with the piece they grabbed. Molt failures, where the shrimp gets stuck halfway out of its old shell, are usually a mineral problem and happen in soft water; keeping general hardness in roughly the 6 to 15 dGH band and providing a calcium and magnesium source (crushed coral, a remineralizer) prevents most of them. Sharp swings in parameters, ammonia or nitrite spikes, and the period immediately after a molt are the riskiest moments, so a fully cycled tank, stable conditions, and slow acclimation matter a lot. Heavy CO2 injection can drive the pH down enough to stress them, and copper-based medications are uniformly lethal to all shrimp.

Bioload

Further reading

• Why your angelfish ate your neons
• Medicating a tank with snails and shrimp
• Keeping shrimp with fish: what actually works