Arrow Crab

Arrow Crab (Stenorhynchus seticornis) – Description & Care Guide

The Arrow Crab, also known as the Spider Crab, is a striking and unusual invertebrate often kept in marine aquariums for its scavenging abilities and unique appearance. Though fascinating, it requires specific care and may not be suitable for all reef setups.

Basic Description

• Scientific Name: Stenorhynchus seticornis

• Common Names: Arrow Crab, Spider Crab, Yellowline Arrow Crab

• Appearance:

  • Long, thin legs and a triangular (arrow-shaped) body

  • Body color varies: tan, golden, or brown with iridescent markings

  • Legs can be reddish, purple, or translucent

  • Extremely long, pointed rostrum (snout)

• Size: Body ~2–3 inches, leg span up to 6 inches

• Origin: Caribbean, Western Atlantic, Gulf of Mexico

• Substrate: Sand or fine crushed coral

• Aquascape: Plenty of rockwork and hiding spaces

Diet & Feeding

• Natural Diet: Scavenger—feeds on detritus, leftover food, bristle worms, and small invertebrates

• Supplemental Feeding:

  • Mysis shrimp

  • Chopped seafood

  • Sinking pellets or carnivore foods

Tip: Feeding them regularly helps reduce aggression toward tankmates.

Care Tips

• Behavior: Nocturnal and semi-aggressive. May prey on:

  • Small shrimp (e.g., cleaner shrimp)

  • Tiny fish

  • Feather dusters and other sessile inverts

• Tank Mates: Best with larger fish and robust invertebrates; avoid delicate or slow-moving tankmates.

• Lifespan: Typically 2–3 years

Caution & Compatibility

• May attack ornamental shrimp (like Lysmata species)

• Can harass small or sleeping fish

• Will eat bristle worms (good for some, bad for others)

• May nip at soft corals if hungry