Prawn Stars

By Rahul G. Kumar Estimated read time: 8–9 minutes

In addition to a number of vividly coloured dwarf caridean shrimp, India is also home to a number of large growing, long armed, and often beautifully coloured river prawns of the genus Macrobrachium. The name Macrobrachium means "big arm," and members of the genus invariably bear a prominent pair of pincers, which are often enlarged in males. Found in the wild in a variety of habitats from hill-streams to brackish water lagoons, these crustaceans make interesting community to species tank only pets, and provide a fascinating alternative to exotic crayfish.

Housing and General Husbandry

Over 50 species of Macrobrachium are reported from India, ranging in size from the roughly 4cm long members of the "red claw" complex, to the over 30cm long giant river prawn. While the smaller members of the genus (up to 5cm), with relatively dainty pincers, can be safely housed in colonies in community aquaria with fishes, the larger members with powerful pincers will hunt down fishes and other invertebrates and are best housed in species only tanks. I do not recommend housing any of these prawns, regardless of size, with long finned fishes such as fancy bettas, guppies or goldfish. Medium sized barbs and loaches make ideal, biotope-accurate tank mates.

The best way to house river prawns, however, is in species tanks. Provide a minimum floor area of 30x30 cm per male for the smaller species up to 7cm in length, and at least 90x30 cm for the medium sized species from 7-15cm in length. The giants of the group require very large tanks, at least 120x50cm per individual, regardless of sex. A single male with a harem of 3-4 females makes the ideal colony. Provide plenty of cover in the form of driftwood, rocks, terracotta pot shards and leaf litter. Stacking pieces of wood, tiles or pot shards to the surface of the water will greatly increase the number of available territories, but be sure to keep the tank covered, as they are good escape artists. Plants are not required, but they are useful for providing cover and surfaces to graze on. Fine leaved stem plants may sometimes be eaten, especially if you have been lax with feeding, but rosette plants are generally safe.

Males are generally tolerant of females in their territories, but will eject other males, often violently. While rare, females can sometimes turn violent, too, and the aquarist must make sure there are sufficient hiding places for all inhabitants in a tank.

River prawns are fairly tolerant of water parameters, with a pH range of 6-8 and temperatures from 22-28C being acceptable. They are opportunistic omnivores, eating everything from algae to vegetables to planarians, snails and carrion. While they can be readily maintained in the aquarium on a diet of pellets (pellets marketed for shrimp farms are ideal), they do much better long term if fed some protein in the form of chopped worms, or shredded fish once a week.

Reproduction

Like other decapod crustaceans, river prawn females are fertilised by males shortly after they moult, and carry the eggs, like bunches of grapes, between their swimming legs, till they hatch. Some species produce smaller clutches of larger eggs, and these develop into miniature prawns; while others produce large clutches of small eggs, which hatch into free swimming larvae that go through many developmental stages before turning into juveniles that resemble the adults. Members of the former group, which include most of the smaller species from hill-streams, are very easy to raise in aquaria, while those of the latter, which grow larger and live in the lower reaches of rivers, often require brackish water and planktonic foods to complete their development.

Acquiring River Prawns

Like other decapod crustaceans, river prawn females are fertilised by males shortly after they moult, and carry the eggs, like bunches of grapes, between their swimming legs, till they hatch. Some species produce smaller clutches of larger eggs, and these develop into miniature prawns; while others produce large clutches of small eggs, which hatch into free swimming larvae that go through many developmental stages before turning into juveniles that resemble the adults. Members of the former group, which include most of the smaller species from hill-streams, are very easy to raise in aquaria, while those of the latter, which grow larger and live in the lower reaches of rivers, often require brackish water and planktonic foods to complete their development.

Acquiring River Prawns

Some species, such as M. agwi and members of the "fuzzy claw" complex are sometimes offered for sale in shops, while many members of the "red claw" complex can be found amongst feeder shrimp. Wet markets are another good place to find interesting river prawns. The interested aquarist will, however, have to collect their own shrimp in many cases. They can be found in most streams across the country with clean, flowing water; under leaf litter or clinging to tree roots and other substrates along the banks. When collecting your prawns, be careful not to bring home specimens visibly infected with parasites (isopods, leeches, worms). Unlike fishes, wild collected prawns must be bagged individually, especially the males, if you want to bring them back home with their limbs intact. Plastic water bottles are ideal for this purpose.

Species Accounts

The most commonly encountered species, and ideal beginner prawn, are members of the "red claw" group (M. lamarrei, M. canarae), so named because their slender pincers are tipped with bright red. Members of this group grow to about 5cm, are found throughout the country, and can be kept in groups with multiple males. They will graze on algae, and are effective at ridding a tank of planarians. Females produce large eggs that hatch into miniature prawns.

Members of the "fuzzy claw" group (M. pilimanus, M. scabriculum) are characterised by the spectacularly hairy pincers on males. Growing to about 8cm, they are rather aggressive and are best housed as solitary specimens or as one male and 2-3 females. The eggs of some species hatch into swimming larvae that complete their development in fresh or slightly brackish water.

Macrobrachium agwi, the candy prawn or bumblebee prawn, is a small, strikingly coloured species from Bengal that is one of the few species commonly available in the trade. This species can be housed in colonies, provided there are plenty of hiding places, and males can establish territories.The lower reaches of rivers and brackishwater lagoons are home to many large growing species with spectacularly long pincers. Macrobrachium striatum is one of the more brightly coloured species, with bright red to brown longitudinal stripes along the body. Growing to about 10cm in length, this species is best housed alone, or as a pair in a large tank. The giant river prawn, M. rosenbergii, grows even larger, to 30cm, and adults sport striking violet claws. They need large tanks, at least 120cm in length, and must be housed alone. Two other large growing species, M. malcolmsonii and M. idella, are commonly encountered in the lower reaches of rivers, but are rather drab in colour; a light grey overall with a few darker stripes and spots. All of these species produce planktonic larvae that require brackish water to complete their development.

Another beautiful, and peaceful, species from the Brahmaputra river, Macrobrachium kulsiense, now in the genus Arachnochium, briefly made an appearance in the hobby in the mid-2000s, but has not been collected in recent years.

About the Author

Rahul G. Kumar has been a keen aquarist for nearly forty years and has successfully managed to spawn over 200 species of fish from all over the world. He has been studying the freshwater fishes of the Western Ghats for the past 20 years, which may, someday, be the subject of a book.

Read the full story

Read the full story in the magazine: Readers who want the complete accounts — including the full authorship, methodology, and discussion behind each of these four discoveries — will find it in the December 2025 issue of The Weekend Aquarist.

👉Buy this issue or subscribe to The Weekend Aquarist to experience the full story.