Description
Several quite different animals are sold as aquarium «crabs», and confusing them is the mistake that causes the most trouble.
Some are fully aquatic, such as the CPO dwarf crayfish (Cambarellus patzcuarensis), which is really a miniature crayfish, or the tiny Thai micro crab (Limnopilos naiyanetri), which lives among moss and bothers nobody. Others are semi-aquatic, such as the vampire crab (Geosesarma), which needs a land area to climb out of the water: in a normal tank filled to the top, it drowns.
Nearly all of them share two traits. The first is that they escape: they climb cables, pipes and silicone with surprising skill, so a lid is not optional. The second is that they are opportunists; they will not hunt down a healthy fish, but a sleeping fish, a freshly moulted shrimp or a fry are within reach.
They are not community tank animals, and that is the expectation to adjust before buying one. Set up properly, with hiding places and dry land when they need it, they are among the most entertaining invertebrates you can keep.
