Emerald Crab

Mithrax sculptus

(50 Reviews)

Emerald Crab
Boasting a vibrant green color, the Emerald Crab is a jewel of the reef tank. It's renowned for its algae-eating habits, making it a natural cleaner and an easy-care addition to any saltwater aquarium.

Emerald Crab

Mithrax sculptus

(50 Reviews)

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Emerald Crab Care Facts

Care Level: Easy
Temperament: Peaceful
Diet: Omnivore
Reef Safe: Yes
Minimum Tank Size: 15 Gallons
Max Size: 2 inches

The Emerald Crab, Mithrax sculptus, are one of the most popular marine crab species for the home aquarium. They thrive in tanks with plenty of live rock and a sandy substrate as the like to graze searching for algae. As voracious algae-eaters, they can be incredibly beneficial members of a cleanup crew. If there is not enough algae or seaweed, they can be supplementally fed with prepared meaty foods. They should, however, be fed regularly to keep them from becoming aggressive towards their tank mates. Emerald Crabs are particularly effective against bubble algae. There is a reason emerald crabs are so popular; they are very easy to care for, require almost no attention, and are effective in in controlling pesky algal blooms hence keeping the tank clean. 

The Emerald Crab: A Molting Feeding Friend for Saltwater Aquariums

The Emerald Crab (Mithrax sculptus) is a delightful and eye-catching addition to saltwater aquariums. With its striking emerald-green color and unique characteristics, this crab has become a sought-after choice among marine aquarists. Let's explore the Emerald Crab's habitat, reef-safe nature, size, lifespan, diet, aquaculture potential, molting process, other common names, and compatible tank mates.

Habitat of the Emerald Crab

The Emerald Crab is native to the warm waters of the Western Atlantic Ocean, ranging from the coast of Florida to the Caribbean and Gulf of Mexico. In the wild, they inhabit rocky shores, coral reefs, and intertidal zones.

Reef Safe and Algae Control

The Emerald Crab is generally reef-safe and poses no threat to corals or other invertebrates. On the contrary, they benefit reef aquariums as they help control unwanted algae growth.

Size and Lifespan

Emerald Crabs are relatively small, typically growing up to 1.5 to 2 inches (3.8 to 5 cm) in carapace width. They can live for two to three years in a well-maintained aquarium with proper care.

Diet and Algae Eating Abilities

In their natural habitat, Emerald Crabs are omnivores, feeding on algae, detritus, and small invertebrates. In a home aquarium, they are excellent algae eaters, helping to keep the tank clean and free from excessive algae growth.

Aquaculture and Sustainability

The Emerald Crab is available in the aquarium trade, and captive-bred specimens are also accessible. Breeding and propagating this crab in captivity have been successful, making it a sustainable and eco-friendly choice for marine aquariums.

Molting Process

Like other crustaceans, Emerald Crabs undergo molting, a process where they shed their exoskeleton to grow larger. The crab is vulnerable to predation and stress during molting, so providing ample hiding spots and a secure environment is crucial.

Other Common Names

In addition to the name "Emerald Crab" or "Green Emerald Crab," this species is also known as the "Green Clinging Crab."

Compatible Tank Mates

Peaceful snail species like Astrea snails or Trochus snails can coexist with the Emerald Crab. Snails contribute to algae control, complementing the crab's role as an algae eater.

Some species of hermit crabs can be suitable tank mates for the Emerald Crab, provided they have sufficient shells to inhabit.

Peaceful blennies are also compatible tank mates. Blennies come in various colors and patterns, adding character to the tank.

Peaceful gobies can cohabit harmoniously with the Emerald Crab. Their small size and diverse range of colors make them great additions to the aquarium.

The peaceful Cleaner Shrimp (Lysmata amboinensis) can be compatible tank mates. They provide an interesting dynamic with their symbiotic cleaning behavior.

In conclusion, the Emerald Crab (Mithrax sculptus) is an enchanting and valuable addition to saltwater aquariums. Its striking appearance and algae-eating abilities make it an excellent choice for reef aquariums seeking a natural and effective algae control solution. Aquarists can enjoy the charm and practicality of these emerald-green gems in their aquatic havens by providing them with a suitable environment and compatible tank mates.

Reviewed by: Damon Guertin on June 27, 2024

Good little purchase

Reviewed by: Chris Von Essen on May 20, 2024

Reviewed by: Dave Bucciferro on May 2, 2024

Reviewed by: Cameron Kreger on March 17, 2024

Ads a nice interest to your tank

Reviewed by: Jim Hauck on March 11, 2024

Healthy upon arrival. They went right to work eating and cleaning!

Reviewed by: Mark Buckley on Feb. 18, 2024


Reviewed by: David Lange on Jan. 17, 2024

Reviewed by: Brian Boyle on Jan. 16, 2024


Reviewed by: Edward A Wilburn on Jan. 12, 2024

All crabs were alive and perfect size

Reviewed by: Sean Boyer on Jan. 2, 2024

Reviewed by: Tim Bunk on Dec. 25, 2023

Arrived healthy. Not large, but when I see him. He's picking food from rock crevices.

Reviewed by: Michael Azoury on Dec. 20, 2023

Reviewed by: Robert Teseo on Dec. 17, 2023

Reviewed by: Erin Holmes on Dec. 17, 2023

Reviewed by: Edward A Wilburn on Dec. 10, 2023

Reviewed by: William Nesselrotte on Dec. 5, 2023

Amazing quality livestock

Reviewed by: Lynn Adams on Dec. 4, 2023

Every reef should have an emerald crab. They are great scavengers. But they’re also pretty much the only natural way to combat bubble algae too.

Reviewed by: Robert Kligerman on Dec. 3, 2023

Reviewed by: Thomas C Hillertz on Nov. 26, 2023

Reviewed by: Andrew Zadrejko on Nov. 23, 2023

Reviewed by: Monika Koch on Nov. 21, 2023

Reviewed by: Oliver Oxenham on Nov. 19, 2023

Nice emerald crabs arrived in good condition and are hiding in my tank somewhere

Reviewed by: Jeffrey Haut on Nov. 16, 2023

Reviewed by: John Ramos on Nov. 8, 2023

Reviewed by: Roy Platt on Oct. 30, 2023

Good size and healthy

Reviewed by: Mary Fetterley on Oct. 26, 2023

Reviewed by: Robert Teseo on Oct. 5, 2023

Reviewed by: Matt Reese on Sept. 24, 2023

Reviewed by: Carrie Payne on Sept. 18, 2023

This guy is awesome

Reviewed by: Phillip Gross on Aug. 30, 2023

Reviewed by: Jean-Paul Haddad on Aug. 20, 2023

Wonderful addition to my tank arrived alive and well.

Reviewed by: Vincent Amrhein on Aug. 15, 2023

Reviewed by: Tommy Mislenkov on Aug. 15, 2023

Reviewed by: Dustin Hirt on Aug. 14, 2023

Doing great

Reviewed by: Ted Glowinski on Aug. 13, 2023

Reviewed by: Corinne Malanoski on July 3, 2023

Good scavenger for algae’s on live rock

Reviewed by: Thomas Lopresto on June 27, 2023

Emerald crabs are always cool! Lost mine to high nitrates last time but replacing my clean up crew, he was first on the list! Fun to watch eat fun to watch grow.

Reviewed by: Jeff Cergnul on Sept. 4, 2017

These crabs appear very busy picking at the rocks and sand. They seems to be good cleaners. They leave my fish and invertebrates alone. Good addition to the tank!

Reviewed by: Brian Bale on March 24, 2017

Very nice little crab. Fun to watch. He has already molted twice since being added, went from a brownish color now turning green.

Reviewed by: Ray on March 19, 2017

Emerald crabs I love my emerald crabs. I have 5 and can always see at least 3 at a time working on my live rock. They are fun to watch, actually it's relaxing! They are out and about and very enjoyable!

Reviewed by: Linda Steele on March 13, 2017

A lot bigger than I was expecting!

Reviewed by: Shannon on Jan. 23, 2017

I received one as part of a reef pack. While it is usually hiding most of the time, it makes appearances once my tank moves to moonlight LED. I have a feeling he is nibbling on the edges of my mushrooms as the other inhabitants are completely reef safe. Arrived happy and healthy.

Reviewed by: Lee Reynolds on Sept. 25, 2016

Came in good condition. Adding rocks to the tank changed water condition, but they survived.

Reviewed by: Michael Joseph on June 14, 2016

Excellent addition to my tank

Reviewed by: Teresa on April 22, 2016

Very healthy very cool

Reviewed by: Kevin Stuart on March 26, 2016

Very fun to watch. I ordered two for different tanks. One was a very light color while the other was very green. The cleanup crew has been doing great at making my tanks look better

Reviewed by: Tazdad08 on March 22, 2016

I received a very healthy, nice size Emerald. He's very active and of course very funny. Love this web site!

Reviewed by: Linda on May 15, 2015

Very interesting addition to a reef clean up crew. Likes to quickly hide in crevices.

Reviewed by: Lia Debettencourt on Nov. 27, 2014

Another family favorite to watch them nibble on their food and climb throughout the tack. Very nimble! They walk around like little boxers and walk sideways in the sand. Doing a great job housekeeping.

Reviewed by: James Fullard on Aug. 23, 2014

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