Aquarium Crabs

Aquarium crabs can be kept for various reasons. Many  species are great scavengers and can help you to keep up the water quality, since they will consume dead and dying organic matter, e.g.  left over fish food and decaying plants. Others are kept chiefly for  their good looks and fascination behaviors, such as the Red-clawed crab  and the Fiddler crab.

The term aquarium crabs is often used to describe a wide range of  different aquatic creatures, but it is actually only the members of the  infraorder Brachyura in the order Decapoda that is  considered true crabs by biologists. The true crabs have five pairs of  walking legs, but the first pair has developed into a pair of claws.  Most true crab species have flattened shells, and the abdomen is  usually folded under the cephalothorax (the first major body section).

As mentioned above, a lot of species that  do not belong to the infraorder Brachyura is still sold as aquarium crabs, since they resemble crabs by being  short crustaceans with thick exoskeletons and ten legs. In this group  of “un-true” aquatic crabs you will for instance find King crabs,  Porcelain crabs and Hermit crabs. King crabs, Porcelain crabs and  Hermit crabs are all examples of specimens found in the infraorder Anomura.  Just like the infraorder Brachyura, the infraorder Anomurabelongs to  the order Decapoda. Unlike the true crabs found in Decapoda, the  Anomura species do however have their last pair of legs hidden inside  the gill chamber, where they are used to clean the gills.

Another species that is often counted among the aquarium crabs is  the Horseshoe crab, even though it is actually more closely related to  spiders than crabs. It belongs to the family Limulidae and  the genus Limulus.  Provide your Horseshoe crab with a water temperature between 72 and 78°  F, a pH between 8.1-8.4 and a dKH between 8 and 12. It is a peaceful  saltwater crab and is therefore popular in reef aquariums.

As mentioned earlier, one of the most popular aquarium crabs among  the species kept for their beauty is the Red-clawed crab. If you want  to keep this crab, you must provide it with surface access. It will  prefer a half-filled aquarium with brackish water and can be kept with  other brackish species, as long as the crab won’t consider them as food  or vice versa. It will survive in freshwater, but brackish water is a  better choice. The water quality should be hard and alkaline. Make sure  that the lid is tight-fitting, since the Red-clawed crab will otherwise  escape from the aquarium. Feed your Red-clawed crab dry food and  vegetable matter. You don’t need a huge aquarium to house this crab,  since it grows no larger than 7 centimeters (2.7 inches).

If you have problems with extensive algae growth in your aquarium,  you add some of the smaller aquarium crabs to combat the problem. Two  popular species used for algae control are the Scarlet Hermit Crab, the  Dwarf Red Tip Hermit crab and the Dwarf Zebra Hawaiian Hermit crab.  Such aquarium crabs are often sold combined with snails that will  consume algae as well.