ARROW CRAB

The arrow crab (Stenorhynchus seticornis) is one of those animals that stops people in their tracks the first time they see it. That impossibly long, pointed rostrum, the spindly legs radiating outward like a daddy longlegs, and the geometric patterning along the body all combine into something that looks almost too strange to be real. Found in the Caribbean and wider Atlantic, it typically hangs around reef structures, rubble zones, and areas with good invertebrate activity in the wild. In the aquarium it behaves similarly, picking its way methodically across rockwork and substrate in search of food. It has a reputation as a bristleworm hunter, which makes it genuinely useful in a reef setup, though it can become opportunistic toward small, slow, or weakened tankmates as it matures and grows more confident. Smaller ornamental shrimp and delicate critters are at real risk in the same system. Given that mix of usefulness and occasional unpredictability, this is probably not the best pick for a beginner reef keeper, but someone with a bit of experience managing a mixed invertebrate community can get a lot of enjoyment out of watching one patrol the tank.