Rock Prawn

Macrobrachium lar

📍 Southeast Asia (Thailand, Malaysia, Indonesia)

Macrobrachium lar, commonly called Rock Prawns, are large freshwater macrobrachium shrimp native to Southeast Asia. They display a translucent to tan body coloration with distinctive long, slender claws and antennae that can exceed their body length. These robust prawns are highly aggressive and territorial, making them unsuitable for community tanks but fascinating for dedicated species-specific setups.

Size3.5"

Min Tank20g

aggressive

Zonebottom

Care Guide

Diet

Rock Prawns are opportunistic omnivores that consume algae, biofilm, detritus, and small invertebrates. Supplement with sinking pellets, blanched vegetables (zucchini, spinach), and occasional protein sources like bloodworms or small crustaceans. Feed sparingly 2-3 times weekly; overfeeding degrades water quality.

Behavior

Macrobrachium lar are highly aggressive and territorial, establishing dominance hierarchons through claw displays and combat. They are primarily nocturnal, spending daylight hours hidden in caves or dense vegetation. Males are particularly combative and will injure or kill conspecifics; solitary housing is strongly recommended.

Breeding

Rock Prawns require brackish water (specific gravity 1.005-1.010) for successful larval development, making home breeding extremely difficult in freshwater. Females produce large clutches of eggs but larvae are planktonic and require marine rearing conditions. Commercial availability is limited; wild-caught specimens are more common than captive-bred.

Tank Mates

Otocinclus

May be predated upon or harassed; only in heavily planted tanks with multiple hiding spots

caution

Amano Shrimp

Risk of predation or aggression; only if tank is very large with abundant cover

caution

Java Moss

Provides essential hiding places and reduces aggression through visual barriers

good

Anubias Nana

Hardy plant that withstands shrimp activity and provides shelter

good

Bucephalandra

Durable plant offering cover without being uprooted by aggressive behavior

good

Common Diseases

Molting Failure / Incomplete Ecdysis

Symptoms

Shrimp unable to shed exoskeleton completely; stuck in old shell; lethargy; death within days

Treatment

Ensure adequate mineral content (GH 8-15); provide iodine supplementation via specialized shrimp mineral additives; maintain stable water parameters; increase humidity in substrate

Bacterial Infection / Shell Rot

Symptoms

Discolored patches on exoskeleton; soft spots; lesions; cloudy appearance; lethargy

Treatment

Perform 25-30% water changes every 2-3 days; maintain pristine water quality; remove decaying food immediately; consider adding Indian almond leaves for tannins; isolate severely affected individuals

Copper Toxicity

Symptoms

Erratic swimming; loss of appetite; color fading; neurological dysfunction; death

Treatment

Use only copper-free medications and fertilizers; perform immediate 50% water change if copper exposure suspected; use activated carbon in filter; avoid tap water with high copper content; test water regularly

Vorticella / Protozoan Infection

Symptoms

White fuzzy coating on body and appendages; lethargy; difficulty molting; reduced feeding

Treatment

Increase water temperature to 26-28 C (79-82 F); perform daily 30% water changes; add Indian almond leaves or peat moss for tannins; improve water circulation; maintain excellent filtration