The Arrow Crab, Stenorhynchus seticornisis, named because of its head and body which looks like an arrow. It has notable long legs. The males are larger than the females. The Arrow Crab's crawls quickly with the help of these long legs, using that advantage to attack small slower moving fish in the aquarium. It is known to feed on bristle worms as well as feather dusters. . Breeding this species is quite difficult in captivity. The Arrow Crab can grow up to six inches and therefore we recommend you to keep it in a larger aquarium. It inhabits small caves or crevices, so lots of rock work is required to be added in your beautiful tank. The Arrow Crab is hardy, long lived invertebrate that can be housed in the reef tank. It is known to attack crustaceans such as Banded Coral Shrimp, and slow moving fish, therefore this crab should be combined with selected species only. The Arrow Crab should be kept singly and should not be kept with similar species, since it may turn aggressive towards other inhabitants.
I've just started my first full marine tank. Have had a little experience with fish-only before. I got an arrow crab, along with a crab/snail kit from saltwaterfish.com (about 50 of the little critters). Two weeks later, there's a small graveyard of the smaller ones in a pile behind a piece of live rock. I think it has to be the arrow - but it's totally worth it. He's creepy, pre-historic, and puts everything in his mouth (then spits out what isn't food). He hides about half the time, and takes harmless swats at fish as they get too close. Add one to your tank.
Fun to watch and great algae eater!
Pretty interesting creature, just be weary. Some arrow crabs have a tendency to hunt other inverts in your tank. I just got my arrow crab a few weeks ago and I've seen him eating 2 of my blue legged hermits.
They will eat anything they can get their pincers on.
Still worth it just so long as he doesn't eat everything else in your tank