Arrow Crab (Stenorhynchus Seticornis)

Also Known As: Spider Crab, Coral Arrow Crab

Compatibility and Behavior
The Arrow Crab (Stenorhynchus seticornis) looks like something that wandered in from another planet. A tiny triangular body perches atop impossibly long, spindly, spider-like legs, and a sharp pointed rostrum, the "arrow," juts forward from the head, the whole thing banded in gold, tan, and blue that catches the light. It moves slowly and deliberately as it prowls the rockwork and slips into crevices, and under dim or moonlit conditions it turns into a genuine conversation piece. The personality, though, comes with an asterisk: think of this one as reef safe with caution. Arrow Crabs are opportunistic carnivores, and while they earn their keep picking off bristle worms and cleaning up leftover meaty foods, a hungry or cramped individual can also harass or outright prey on very small fish, delicate shrimp, and other tiny inverts. That makes it a poor match for ornamental shrimp or timid little fish, but a fine choice for a keeper who wants a more predatory cleanup crew member and houses it with robust tankmates. It tends to coexist reasonably well with larger fish, snails, and hardy hermits.

Aquarium Requirements
This is a crab built for rockwork, so an established tank with plenty of caves, overhangs, and crevices to squeeze into and hunt through matters more than raw gallons. A single crab can work across a wide range of tank sizes as long as the footprint offers good structure and hiding spots. Moderate flow is the sweet spot, letting food settle into the nooks it can reach with those long legs rather than blasting it off its perch. Keep salinity stable and oxygenation good, and feed meaty foods regularly, such as frozen mysis, chopped seafood, or sinking carnivore pellets, which keeps it satisfied and noticeably less interested in bothering tankmates. One practical note given its size and reach: secure loose frags and top-heavy rockwork it might dislodge while clambering around.

Specifications
Approximate Size: 1.5–3.5" (leg span considerably larger than the body)
Diet: Carnivorous scavenger; leftover meaty foods, worms, small invertebrates, and prepared carnivore foods
Origin: Western Atlantic and Caribbean
Care Level: Moderate
Reef Safe: With caution
Temperament: Semi-aggressive
Special Considerations: Opportunistic predator that may prey on very small shrimp (such as Sexy Shrimp), tiny fish, and delicate inverts, so avoid keeping with ornamental shrimp or timid small fish; can dislodge loose frags or top-heavy rockwork while climbing