marine invert of the month
photograph by the author
Common Names: Harlequin shrimp,
clown shrimp, painted shrimp, dancing shrimp
Range: East Africa, the Red Sea to Indonesia,
northern Australia to Hawai‘i, and Panama
and the Galapagos Islands
Natural Environment: These exceptionally pretty shrimp,
which reach about 2 inches in length, inhabit shallow protected
inshore areas and are commonly found among coral branches. They
often live as mated pairs, a situation in which they can become
quite territorial. Females are larger than males and have blue-tipped
abdominal legs, while the legs of males are transparent. Males also
lack the blue/purple spots under the tail that appear on females.
Captive Care: These shrimp can do well in reef systems
provided you are willing to meet their unique dietary needs—they
will only eat live sea stars. Note the emphasis on live, as they will
not touch a dead or defrosted frozen sea star. A star about 4 to 6
inches in diameter will be consumed in about four weeks.
Watching a living sea star torn apart and eaten may not be
something you want to witness in your home aquarium! In fact,
the shrimp will turn over the star to immobilize it and begin
nibbling from its leg tip inward to the central disc. Besides being
carnivorous, they are very territorial, so only one or a mated pair
can be kept in the same aquarium.
They are not overly fussy about which sea stars they will consume,
although I have found that they especially like the blue Linckia
laevigata, which is almost as expensive as they are! They will also
eat small chocolate chip stars Protoreaster nodosus, those in the genus
Fromia, and some of the sand-sifting stars. Luckily, they will also
consume the Asterina stars that often proliferate among live rock
and are therefore quite useful in controlling the population of such
creatures—if one can live with their gruesome feeding behavior.
Keep in mind that all shrimp should be slowly acclimated to their
new surroundings, as they have a tendency to go into shock when
entering an aquarium where water parameters are even slightly
different from the shipping container. Temperature and especially
specific gravity should be the same before transferring them to their
Contrary to what you may have heard, shrimp of any kind should
never be given a freshwater bath to kill parasites prior to being
added to the aquarium. It will kill them, as they are very sensitive
to changes in osmotic pressure.
As with all shrimp, calcium, iodine, and magnesium are essential
for molting, and none of these should dip to low levels. Molting is
the process of shedding the shrimp’s shell-like exoskeleton, which
allows the shrimp to grow. To grow larger, a shrimp must shed this
exoskeleton, as it will not stretch. A new exoskeleton continuously
develops underneath the old one, which is shed once the new
exoskeleton is ready.
When the process completes, the exoskeleton splits open and
the shrimp climbs out. Then it takes up water, stretching the
folds out of the new soft covering to fit its now larger body.
The new covering then hardens. Keep in mind that they are
defenseless at molting time and need secure hiding places that
predators cannot reach.
Water Quality Requirements: Calcium 380 to 430 mg/l,
alkalinity 2. 5 to 3. 5 meq/l, pH 8. 1 to 8. 2, specific gravity 1.024 to
1.026, and a temperature range of 75° to 85°F.