Minimum Tank Size: 10 Gallons (37 Liters)
Care Level: Easy
Water Conditions: PH 6.5-7.5 Moderately Hard to Very Hard
Temperature: 60-80°F (15-26°C)
Maximum Size: 2 inches (5 cm)
The Amano shrimp (Caridina multidentate), also know as Yamato shrimp, Japanese Shrimp, and algae shrimp, are a popular species of shrimp, well known for their ability to consume algae. It was previously known as Caridina japonica, but was renamed to Caridina multidentate in 2006.
Amano shrimp are native to Japan and Taiwan and are found in freshwater marshes and swamps. It is possible they are also native to several other countries including Madagascar and Fiji, but there are conflicting reports as to whether the shrimp found there are the same species.
These shrimp stay relatively small in the home aquarium, and usually only grow to a maximum length of 2 inches (5cm). Well cared for Amano shrimp can live for up to three years, though two years seems to be more average.
Amano shrimp should be kept in aquariums that are at least 10 gallons (37 litres), and any tank containing them should be heavily planted, with numerous hiding places for them to seek shelter in. It’s important to only add them to mature tanks, as algae growth is important to their health – something that can’t always be found in newly established aquariums.
These shrimp live in vast troupes in the wild, and they can happily live in dense populations in aquariums. However, it’s rare to keep more than a handful of these shrimp together, and most tanks will only have a few shrimp to help keep the algae growth under control.
It’s important to house Amano shrimp will small, non-aggressive fish. Many species of fish will attempt to prey on them, and even ones that are incapable of swallowing them whole, will often tear off body parts. While they can regrow lost limbs, it’s best to prevent injuries which could eventually be fatal to shrimp.
Some people claim that they can damage aquatic plants, but there seems to be little evidence to back this up. Many aquarists, myself included, have used them to control algae in showpiece planted tanks, and their tireless work helps to keep plants free of unsightly algae. With that being said, they will eat dead or dying leaves, so this may be where the myth originated.
Amano shrimp can handle current in their tank quite well, so a hang-on-back filter is still an excellent choice for their aquariums. When choosing a hang-on-back, the Aquaclear Power Filter is one of the best choices you can make. Not only is it incredibly durable, but it usually lasts for years with virtually no problems. I use them on the majority of my tanks, all without incident.
While many people believe these shrimp consume nothing but algae, they are in fact omnivores, and their diet should regularly be supplemented with blanched vegetables and sinking fish food. But if they are kept with fish, they will scavenge any missed food, as well as any algae and detritus in the tank. So, they don’t need to be fed very often.
The best food to feed these shrimps are sinking Hikari Algae Wafers, which provide all the nutrients they need. These shrimp can also regularly be offered blanched vegetables, like zucchini, cucumbers, and broccoli, although unless they are kept in groups large enough to completely consume the vegetables, the uneaten portion of the vegetables will have to be removed after 24 hours. This prevents the decaying vegetables from fouling the aquarium water.
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It is relatively easy to sex Amano shrimp, as the females have a more elongated lower row of dots than the males. And while sexing them is easy, breeding them isn’t nearly as simple, and it takes a truly committed aquarist to breed these shrimp. There are few reports of these shrimp even mating, never mind the larvae being raised to adulthood.
In the wild they mate in freshwater, but the eggs are released into brackish water, and spend much of their larval stage in salt water. As they grow, they will eventually return to freshwater, and because of this lifecycle, it is difficult, though not impossible, to breed these fish in captivity.
Breeding is quite a frantic affair with these shrimp, and the females will release a pheromone into the water, making the males desperately search the tank for them. It’s not unusual to see several males piled on top of one female, though the female will only mate with one male.
The female will usually carry the fertilized eggs for close to six weeks, and then the larvae will be released into the water. The larvae will then need brackish water in order to grow, and if they don’t receive it, they will quickly die.
It’s important that you don’t add adult shrimp to a brackish water tank in the hopes of rearing the larvae in the same tank. The adults are unable to tolerate salt, and even at low levels, it can be fatal to them. Therefore, the adults would have to be removed from the breeding tank, and the salinity of the water would have to be slowly increased for the larvae. Unfortunately, no information is available about the larvae’s preferred salinity.