Dwarf Freshwater Shrimps: An Overview
When I was a youngster, my grandparents had a small aquarium in their home. The nearest aquarium store to them was in the back corner of Woolworths, so unlike the aquarium we had at my parents’ home, my grandparents’ tank was routinely filled with whatever Woolworths got in. The most memorable thing about the tank is how often it was bizarrely stocked.
Scissortail rasboras (Rasbora trilineata) featured prominently, as did various snails. The tank even briefly held an irresistibly cute oscar (Astronotus ocellatus). But the most unusual thing was my grandmother’s penchant for adding freshwater shrimp. These weren’t anything fancy, just mostly clear, somewhat yellow critters that crawled around the bottom of the tank and were usually sold as either “ghost shrimp” or “whisker shrimp.”
Just the same, they captured my imagination. If to me fish tanks represented another world with animals that glided effortlessly through their universe, the shrimp were the true aliens, with multiple legs, antenna, claws, and a total lack of skeleton—something truly “other.” Today, the generic clear shrimp you’ll find in pet shops have mostly moved from the display tanks to the feeder tanks in the back, having been replaced by myriad varieties of shrimp in colors my grandparents would never have imagined.
The shrimp at the center of the new craze is undoubtedly the cherry shrimp (Neocaridina davidi). To channel my inner taxonomist, I would say this shrimp has undergone something of a nomenclatural journey, as it can be found in various resources under several different names. Much of the literature describes it as Neocaridina heteropoda, based off a 2002 description by Liang—indeed, this is probably the most common name you’ll see cherry shrimp listed under. However, a 1918 description of this shrimp as Neocaridina denticulata has been cited by numerous sources, and this name is sometimes used. The earliest, correct description, however, is in 1904 as N. davidi.
These are relatively small shrimp, reaching about 1½ inches (4 cm) at most. Males are often half that size. The natural shrimp isn’t much to look at—they’re kind of a brownish green, and especially because of their size, you’d be forgiven for overlooking them. An interesting mutation leads to the mottled color being replaced by red, and depending on how far this mutation goes, they can range from sort of red to solidly bright red. In addition to the red, other mutations have occurred that result in orange, yellow, black, green, blue, and even purple.
These various strains are given names based on their extent and color. There isn’t really a consensus to the naming schemes, and a lot of this is marketing-based. While the basic cherry shrimp is a fairly low-priced animal, some of the more unusual and vivid types of freshwater shrimp have drastically higher prices. I’ve often joked that some are more expensive than a dozen much larger shrimp, in sauce, at a fancy restaurant. As such, there’s a lot of incentive to give shrimp strains catchy, and uniquely different, names.
Aquarists keeping multiple strains of these shrimp should be aware that they are just that: strains. They are not different species. This is the same as, say, guppies. It doesn’t matter if it’s a blue guppy or a red guppy; it’s a guppy. They’ll quickly crossbreed, and you’ll get a very quick lesson in Mendelian genetics. Various colors are dominant, but as they’re mixed and diluted, subsequent generations will soon revert to the plain brown shrimp. For the sake of convenience, we’ll use “cherry shrimp” as a common name for all varieties of N. davidi. Note that, as with most animals, more selectively bred individuals tend to be more delicate, but the care is otherwise the same regardless of your shrimp’s color.
Care for the cherry shrimp is ridiculously simple and can almost be summed up as “just add water.” These are small animals, and even a small aquarium will suffice, though they’ll do just as well in larger tanks. Slightly acidic to neutral water is ideal, and the water must have some hardness to it. They’re not at all particular about water chemistry, provided extremes are avoided. Generally, they’re particularly popular among planted aquarium enthusiasts, but a planted tank is not required. They’re omnivorous and will nibble algae from live plants—or from plastic substitutes—as well as scavenge through your substrate. Of course, they cannot survive as strict scavengers, and supplemental foods must be given. Essentially, any sinking food works.
Provided you have males and females, you’ll breed them. Sexing the cherry shrimp is quite easy. Mature males are smaller and generally less colorful than females. Females have prominent swimmerets (attachments on the underside of the tail) that are used to hold the eggs. You’ll often see females carrying clutches of eggs underneath their tails. These eggs soon hatch into miniature shrimp and will rapidly develop into adults.
Tankmates for the cherry shrimp should be chosen with care. Obviously, when placing anything with small shrimp, it should not be large enough to eat them. Remember that the babies are small, a quarter of the size of adults, and fish are apt to pick them off. This may or may not be a problem: the shrimp are relatively fast breeders, and with adequate hiding places, many of them will reach adulthood. More important, the males are half the size of the females, if that, and a population of shrimp can become all female very quickly if there’s a tankmate eating the smallest ones.
Bee ShrimpIn addition to the cherry shrimp, many other colorful species make it into the trade. Second to the cherry shrimp is the bee shrimp (Caridina cantonensis). Like the cherry shrimp, the bee has been bred into a number of colorful varieties, the best known of which is the crystal red shrimp. Many of the varieties of bee shrimp have the word “crystal” in their name, but additional varieties commonly traded include the blue bolt shrimp, tangerine tiger shrimp, and panda shrimp. As a rule of thumb (with the caveat that it’s a generalization), shrimp varieties with the words “bee,” “crystal,” “tiger,” “bolt,” or “panda” will be this species.
The red crystal, red bee, or red crystal bee variety is a striking type of freshwater shrimp with a red-and-white body. Varying amounts of red and white have led to a grading system, with higher points going to shrimp with more solidly colored and more white bodies (though for the highest grades, they must have both).
Bee shrimp are a lot more sensitive than cherry shrimp to water conditions. They demand slightly acid to neutral pH, and relatively soft water. They’ll also appreciate it a bit on the cooler side, around 68° to 72°F (20° to 22°C). Like cherry shrimp, all the varieties of bee shrimp are the same species, and they will crossbreed, resulting in diluted strains. They will not, however, crossbreed with cherry shrimp varieties. Care and breeding are otherwise identical to that of the cherry shrimp.
One of the less commonly encountered dwarf shrimps is a close relative of the bee shrimp known as the Babaulti shrimp (C. babaulti). Like the bee shrimp, they’re striped, but the stripes tend to be bolder and more prominent. There are fewer varieties of this shrimp, many of which have “Babaulti” in their name. As a relative of the bee shrimp, they should not be mixed.
The island of Sulawesi, formerly known as Celebes, is home to one of my personal favorite shrimps, C. dennerli, the stunning cardinal shrimp. This is a brilliant red shrimp covered with white dots, and marine aquarists would be forgiven for mistaking it for a member of the genus Lysmata.
They’re found in Lake Matano, an inland body of water in Indonesia. In this same region are found many other striking red shrimp, such as the pinstripe shrimp (C. striata) and the harlequin shrimp (C. spongicola). These are much more sensitive, owing in part to their long journey to our aquariums. They’re generally intolerant of dissolved organics, high nitrates, and poor husbandry. This is also a warm water lake with temperatures hovering around 88°F (30°C). Curiously, many reports of water conditions there state a high pH (8.2 or higher) and a very low conductivity—the water has a high pH but remains soft. This can be mimicked in the aquarium by adding a base, such as sodium hydroxide (NaOH) to soft water, cautiously.
Assuming you can meet their water conditions, these dwarf shrimp are not particularly difficult to care for. They’ll breed similarly to red cherries or bee shrimp, and it seems that tank-bred shrimp are much more adaptable than wild caught, with the requirement for high pH evaporating; softer water is still generally required.
The genus Caridina contains one final shrimp that is of particular interest to aquarists, C. multidentata, known as the algae shrimp or the Amano shrimp. A handful of other species of Caridina are collected with these and offered under the same name. This is a less colorful shrimp, and it is fairly nondescript, though adults have a pleasing pattern of brown or red dots along the body.
Amano shrimp are primarily used in planted aquariums to pick algae from plants and such. They’re omnivorous and will also scavenge, but the bulk of their aquarium diet is based on algae. They should certainly have this supplemented with a high-quality shrimp food, or algae pellet. When insufficient food is present, the Amano shrimp does have a tendency to go wandering (as they will if they don’t like the aquarium condition), as in straight up and out of the tank. They are accomplished jumpers, and I’ve found them quite some distance from the tank.
C. multidentata are generally not picky about water chemistry, though they can be sensitive to poor water quality. They’re a larger shrimp, and fully grown adults can push 2 inches (5 cm). Unlike the other varieties of shrimp discussed thus far, the Amano shrimp cannot be bred successfully in the average home aquarium. They’ll breed, and do almost constantly, but the larvae do not develop. In the wild, they’re found in areas connected to saltwater. Their larvae are released and washed into brackish estuaries, where they develop and migrate back into freshwater. This is nearly impossible to mimic in the average aquarium (particularly as the adults are sensitive to salt), though a handful of aquarists, including me, have done it. Fortunately, they’re anything but rare in the wild and collection of them is not problematic.
Ghost and Grass Shrimp
The genus Palaemon and its sister taxon Palaemonetes (as well as a handful of other genera) are known collectively as ghost and grass shrimp. It’s likely that these genera are not distinct and will be merged in the future. This is a cosmopolitan grouping, and members are found in freshwater, brackish, and marine environments. The ghost shrimp we see in the United States are likely Palaemonetes paludosus, as this is the species found naturally in Florida, where they’re farmed.
These small, clear shrimp are important food items in the wild, and they’re often used for that purpose in the trade. Ironically, many pet stores have two tanks of them, one in the back for feeders, and one up front at six times the price for pets. They probably came in the same bag. P. paludosus is often found in brackish water and will even survive in marine water. As a pet shrimp, they’re an intriguing, neat species, particularly since they’re almost invisible. Generally, their eyes and stomach are the only things you’ll see.
Ghost shrimp are quite indestructible. Essentially, any water conditions will be fine for them. They’ll feed on suspended matter in the aquarium and also eagerly eat algae, detritus, and any fish food offered to them. They’re similar in size to cherry shrimp, if not a little bigger, and as such should not be kept with larger fish. They can safely be mixed with other varieties of shrimp.
Ghost shrimp are one of the more traditional species of dwarf shrimp offered, as are the whisker shrimp. The whisker shrimp is a catchall name applied to several types of shrimp, which often include ghost shrimp. More typically, the name is applied to small members of the genus Macrobrachium, which is closely related to ghost shrimp. However, the members of the genus Macrobrachium tend to get larger, and depending on which species of Macrobrachium you have, perhaps significantly larger.
The smaller species reach a maximum of 3 to 4 inches (7.5 to 10 cm). Whisker shrimp tend to be forgiving of water conditions and will generally breed on their own in the aquarium, provided males and females are present. However, they tend to be aggressive with each other and must be given adequate space. Males will often kill one another, though they’ll generally tolerate females. They cannot be mixed with other species of shrimp, as they are aggressive and will eat them. They’ll sometimes eat small fish, though this is rare with smaller species.
Larger members of the genus Macrobrachium are actually farmed for food, and some large species make it into the trade, often under the name “long arm shrimp” (a rough translation of Macrobrachium) or something like “blue claw shrimp.” The genus Macrobrachium is poorly understood, so identifying a specimen to species level is incredibly difficult.
As the name implies, adults of these species have very long “arms,” with the claws greatly extended out from the body. The arms can be twice the length of the rest of the body, depending on species. Some of these shrimp enter the trade accidentally, occurring as by-catch with other types of freshwater shrimp, though several are purposefully collected as well. Most species will have a body size of about 4 to 6 inches (10 to 15 cm), though some species will reach a full foot (30 cm).
Males of the long-arm shrimps will actively kill each other, though they’re generally peaceful toward females. While the long arms remind me of the oversized claws on fiddler crabs (Uca spp.), they’re not a display item—the shrimps will actively use these claws to battle one another, pick detritus or other food items, and prey on fish. As such, they should not be kept with anything they can snag and eat. Fish tankmates should be active, fast, and generally larger.
Like the genus Caridina, long armed shrimps include species that need saltwater to breed and many that breed in pure freshwater. Most of the ones that make it into the trade purposefully are able to breed in freshwater.
The genera Atya and Atyopsis are known as the vampire or bamboo shrimps. Of particular interest to aquarists are Atya gabonensis and Atyopsis molluccensis. Both of these freshwater shrimps are similarly described as having a dark brown body with some striping or markings and an adult size of roughly 5 inches (13 cm). The most striking features of both are the feathery fans located at the front of the shrimp that are used to filter material from the water.
These are not aggressive or predatory species, and they should not be housed with anything that might bother them. They do need an area of high current, where they’ll often be found filtering the water. Mine are usually found hanging on the output of a canister filter. They’ll remove finely powdered foods, zooplankton, or even crushed fish food from the water column, all of which should be directed at the shrimp to keep it properly fed. Because of their special dietary requirements, these shrimps are best left to advanced aquarists.
The genus Caridina alone contains hundreds of species. Add to that its sister taxon, including Neocaridina and others, and the number of dwarf freshwater shrimp becomes nearly impossible to keep straight. A word of caution to aquarists: many dealers can’t, or don’t, keep these species (or even genera) straight.
I have seen availability lists with both N. davidi and N. heteropoda, with each name describing different strains. While some of this may be naiveté, most is marketing. This is made worse by some dealers who mix up strains and list a variety of C. cantonensis as a variety of N. davidi. Make sure you do your research if you are planning to mix any varieties of shrimp—while a species of Caridina won’t cross with a species of Neocaridina, you want to ensure that you actually do have different genera to avoid hybridization in your tank.
The upside to all of this is that there are countless varieties of shrimp available to hobbyists, in a rainbow of colors. The sheer diversity of shrimp in the hobby is mind-blowing, especially when you consider how recently they appeared in the mainstream hobby. The fascinating ghosts and whiskers still have their place, but they have largely been pushed aside for these beautiful shrimps. I’d like to think that my grandparents would have some of these new, colorful shrimp in their tank today.