Usually added to join the janitor family in reef aquariums, crabs are indeed of help in cleaning the wastes and leftover nutrients. For large tanks there indeed has to be one or two of these cleaning crew to prevent algal blooms. However, not all crabs are reef safe. Some grow enormously, some eat up the coral tissues, some are aggressive enough to harm the invertebrates and some are difficult to keep in aquariums. While buying crabs for your reef tank it is important that you consider briefly the species, research on them and assure that they are reef friendly. Also it is important to determine how many of these critters you should accommodate in your reef tank. Hermit crabs are mostly apt for reef tank but not all hermit crabs are reef friendly. Take a look at some crabs that are reef compatible:
1. Dwarf Blue Leg Hermit Crab
They are small sized and visibly attractive with blue colored body. The care level is easy and they feed on all kinds of algae including the red slime algae that cause major disaster. In nature also they are found in coral reefs and cause no harm to them living on their bases. They are small enough to get into tiny holes and scavenge on all hidden algae and nuisance. They are good for reef tanks as they sift the sand as well. Usually they will feed on algae and if there are no algae you can feed them with seaweeds.
2.Dwarf Red Tip Hermit Crab
Also called Mexican hermit crab for their origin in Mexico, these are characterized by red on their tip and legs. They are hardy and easy to maintain. They are detritus eaters and are chiefly fond of filamentous, hair, and slime algae, as well as the dreaded cyanobacteria. They don’t grow much and the adults might grow only up to two inches. They are great scavengers and completely reef safe. They are peaceful in nature and apt for reef tanks
3.Green Emerald Crab
Their shiny green body has made them a favorite scavenger of many aquarists. They nosh on irritant algae like hair and bubble algae as well as on meaty leftovers and organic food. Their flat tipped pinchers are of help for grabbing algae and other food. They are night scavengers and prefer to stay hidden during day. Though they are found to be reef safe on rare accounts they have been reported of picking polyps off SPS corals and some Purple Gorgonians. If you plan on keeping this crab in your reef tank it is recommended that you begin with one and not more until you are assured of their compatibility with the tank mates.
4.Scarlet Hermit Crab
The scarlet hermit is another reef compatible species of hermit crabs that are small in size, eat algae, sift the sand and help in keeping the tank clean. They are peaceful towards tank mates and prefer to stay hidden during most hours of the day. They are good scavengers and hunt out the hidden nuisance from tiny holes. No damage to corals or other marine creatures have been found by this crab.
5.Arrow Crabs
These are hardy, live longer and are of no harm to tank mates. For its long body and arrow like head it is also called the spider crab. They feed on all decaying or left over foods, as well as hunt bristle and flat worms which make them highly in demand for nuisance control in any reef aquarium. They are an interesting species to study on and are very adjusting to water conditions.
6.Spotted Porcelain Crabs
The attractive spotted porcelain crabs are light blue in color and covered in small red spots, with orange tipped legs. They look extraordinarily elegant in reef tanks and are highly compatible with corals and other marine creatures. They frequently clean the water for planktonic food, and also scavenge for larger meaty scraps. You can give the crab small bits of fish, shrimp or meaty food, as well as foods designed for filter feeders.
7.Zebra Hermit Crab
The white and black stripes on its body make them an exclusive addition to reef tanks. They are reef safe and good scavengers. The enlarged claw unlike other dwarf hermit crabs might look scary but are of no harm to reef mates. They eat up all the nuisance dwellers and uninvited algae like the red slime. If the tank is clean, external feeding might be required.
8.Halloween Hermit Crab
They have the most interesting color pattern on their body, with orange and black strips all over, making them in demand for reef tanks. They wear abandoned shells to guard them from predators. They hike on live rocks and hunt out all the hidden algal blooms. They are good scavengers and reef safe with no extra maintenance needed.
9.Anemone Crabs
They have red or brown blotches all over their body and are reef safe with no extra trouble. Like the clown fish, this crab has developed resistance to anemone stings. They live in pairs under the protection of anemones. It may try to preserve its area from clownfish that try to establish themselves among the anemone, although the clownfish generally reigns. It eats planktonic food and mucus from the anemone.
There are many more reef compatible crabs and even more non compatible crabs that sellers do not tell you about. Research well before buying and start with one or two.