Crawling its way into the AquaNerd Picture of the Week is the weird and unusual Arrow Crab (Stenorhynchus seticornis). This particular critter is found in a lot of reef aquariums, as people just love to watch these proverbial crabs on stilts walk around the tank and pick at the rocks looking for food. While these crabs are generally accepted as reef safe and potential pest removers, what a lot of hobbyists don’t realize is that this crab can cause some serious harm. They can perch up on rocks and wait for unsuspecting fish and shrimp to wander by. When the prey is in a suitable location, the crab will reach down with its claws and attack, eventually consuming the unfortunate fish or invert and moving on to the next victim.