Crabs

It is easy to see why the Scarlet Reef Hermit Crab is one of the most popular reef maintenance animals. Paguristes cadenati is very hardy and requires minimal care in a well-established system. More importantly, however, these small hermit crabs have a voracious appetite for detritus and algae. In fact, they are particularly fond of nuisance algae of the filamentous, hair, and slime varieties, as well as cyanobacteria. Finally, unlike some hermit crabs, most Scarlet Reef Hermit Crabs are very peaceful towards their tankmates. Also known as the Red Reef or Red Legged Hermit Crab, the Scarlet Reef Hermit Crab is named for its bright red legs, which are contrasted by their yellow face. Native to the reef faces and coral rubble of the Caribbean and Western Atlantic, these active scavengers can consume large amounts of animal matter and algae. Despite their large appetites and constant feeding habits, the Scarlet Reef only grows to an adult size of 1-1/2" in length. In the home aquarium, Paguristes cadenati is best kept in an established reef system with ample algae supplies. However, they will eat almost anything, including fish food and invertebrate diets. If algae levels are insufficient, supplement their diet with dried seaweed and other marine foods. Like other hermit crabs, an ample supply of empty shells should be available for the Scarlet Reef Hermit Crab to move into as they molt and grow. As with all invertebrates, they do not tolerate copper-based medications and extreme fluctuations in water parameters. Also, take special care to ensure an invertebrate-friendly environment free of predators.

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Hermit crabs such as the Calcinus Laevimanus are very interesting animals and good cleaners, which is why they are often part of the cleanup crew that enters the aquarium first. The animals themselves only grow to about 2 cm, but because they have no protection themselves, they look for a snail shell to live in. As the animal grows, it will always look for a larger house, which must also be present in the aquarium. They often also take shells from snails, such as the Turbo Fluctuose, by pulling the snail out of the shell.

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Hermit crabs such as the Calcinus Gaimardii (Dwarf hermit) are very interesting animals and good cleaners, which is why they are often part of the clean-up team that first enters the aquarium. The animals themselves only grow to about 2 - 3 cm, but because they have no protection themselves, they look for a snail shell to live in. As the animal grows, it will continue to look for a larger home, which must be present in the aquarium. They often also take houses from snails such as the Turbo Fluctuose, by pulling the snail out of the house. This hermit does not grow very large and is therefore very suitable for nano aquariums.

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The Macrocoeloma trispinosum, commonly known as the Decor Crab, is a fascinating crustacean that disguises itself by attaching algae, sponges, or dead coral pieces to its carapace. Native to the reefs of the Western Atlantic and Caribbean, this crab is an excellent detritivore, helping to clean aquariums by feeding on organic waste and algae. However, due to its opportunistic behavior, it should be monitored in reef tanks, as it may occasionally prey on small invertebrates or soft corals.

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The Spider Decorator Crab, also known as Camposcia Decorator Crab or Decorator Crab, is a member of the Majidae family of spider and decorator crabs. It decorates its brown body with sponges, shells, rocks, and other items as a method of camouflage. It is nocturnal, hunting at night. In the reef aquarium, it harvests algae, soft corals, and invertebrates to adorn its shell. This activity may cause harm to some soft corals, but in the large reef aquarium, this activity actually helps spread and propagate these same corals throughout the aquarium. The diet of the Spider Decorator Crab should include meaty foods such as chopped fish and clams.

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The Pom Pom Crab is white to tan in coloration and has darker markings covering the body which serve as camouflage for the crab. This crab carries an anemone in each claw which it uses for defense. Besides defense, the crab will also use the anemones to mop up food off of the rocks and substrate. The Pom Pom Crab is an interesting addition to an aquarium with its anemones in each hand. It raises these anemones at would be predators and aids in cleaning the aquarium of any left over food and detritus. Caution should be used when adding this crab to a reef aquarium as the anemones could sting sessile invertebrates and corals. The damage that could potentially be caused by these tiny anemones that come on each claw would be minimal due to their very tiny size. The diet of the Pom Pom Crab should include meaty foods such as mysis shrimp, chopped fish and clams.

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The Horseshoe Crab is greenish brown to light tan in color. The dorsal part of the body is rounded, and it has a long spike for a tail. The Horseshoe Crab is really not a crab, but more closely related to spiders and mites, belonging to a group of animals called chelicerates. Horseshoe Crabs can grow quite large. The female horseshoe crabs usually grow larger than the males, with their body reaching a maximum size of 12 inches in diameter. When small, they are very efficient scavengers and are great for aerating and maintaining sand beds. The Horseshoe Crabs dig through sand and gravel in search of worms and any organic debris. It will move the substrate around almost nonstop in its search for food. They are reef safe, but when they attain a large size, can be harmful to fish and invertebrates, especially worms and clams. Although it may find some food scavenging, its diet should be supplemented with meaty items such as pieces of squid and shrimp.

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The Halloween Hermit Crab, with its vibrant orange and red banding, stands out as a member of your aquarium cleanup crew. Originating from the Hawaiian Islands, the Halloween Hermit Crab boasts attractive color variegation and is a beautiful accent to the marine aquarium. The Halloween Hermit Crab is a very useful aquarium cleaner that helps maintain a healthy aquarium environment by eating any left over food that may settle on the substrate. Adding further value, the Halloween Hermit Crab is known to efficiently eat algae including green hair algae and cyanobacteria. It also provides a valuable service of aerating aquarium substrate by sifting through the sand. Be aware that as the Halloween Hermit Crab attains a large size, this lumbering scavenger may disrupt rockwork or corals in reef aquariums. The Halloween Hermit Crab lives in abandoned snail or triton shells and may resort to attacking and eating a snail so it can use the shell for its home. To prevent this from happening, provide the Halloween Hermit Crab empty shells of assorted shapes and size. If there is an insufficient amount of algae present, the Halloween Hermit Crab will need to be fed dried seaweed, as well as meaty items such as mysis shrimp.

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The Arrow Crab (Stenorhynchus seticornis) is a unique and eye-catching marine invertebrate known for its extremely long, thin legs and pointed body shape. It is a popular addition to reef aquariums due to its unusual appearance and scavenging behavior. Native to the Western Atlantic and Caribbean reefs, the Arrow Crab spends much of its time hiding among live rock, caves, and coral structures, coming out mainly at night to feed. Behavior & Diet: The Arrow Crab is an opportunistic omnivore and scavenger. It feeds on: Leftover fish food Detritus and organic waste Small worms and bristle worms (in some cases) It can help contribute to tank cleanliness, but it is not a primary cleanup crew member like hermit crabs or snails. Care Requirements: Provide plenty of live rock and hiding spaces Stable reef aquarium conditions Feed if natural food sources are limited Keep with compatible, non-aggressive tank mates Important Notes: Can be semi-aggressive toward small or slow-moving fish and invertebrates May prey on small worms and weak organisms Not fully reef-safe in all setups—monitor behavior carefully Best suited for experienced reef keepers

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