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Emerald Crab
Please Note: Due to variations within species, your item may not look identical to the image provided. Approximate size range may also vary between individual specimen.
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Emerald Crab (Mithraculus sculptus)

Quick Stats

Care Level Easy
Temperament Semi-aggressive
Color Form Green
Diet Omnivore
Reef Compatible Yes
Water Conditions 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025
Max. Size 2½"
Origin Caribbean
Family Majidae
Supplements Calcium, Magnesium, Iodine, Trace Elements
Compatibility View Chart
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The Emerald Crab is well respected for its scavenging ability. It will enthusiastically feed on uneaten meaty foods and many types of nuisance algae. Unlike many other animals, Mithraculus sculptus will eat bubble algae and helps clean your aquarium of these algae. Its distinct, flat shiny green body and hairy legs easily identify the Emerald Crab.

Native to the reefs of the Caribbean, the Emerald Crab is nocturnal and hides in caves and amongst rubble during the day. In the home aquarium, this member of the Majidae family requires a well-established aquarium with plenty of rockwork and hiding places. Once familiar with its surroundings, the Emerald Crab will venture out of hiding during the day to forage on algae.

Care needs to be taken to ensure an ample supply of food is available for the Emerald Crab. Many aquarists supplement the Emerald Crab's diet with dried seaweed and chopped meaty foods, such as shrimp, as well as a quality pellet fish food.

Otherwise, this opportunistic feeder may turn to corals, invertebrates, or small fish for a food source. However, when well fed, most Emerald Crabs are very tolerant of their tankmates and highly compatible in reef environments. Like other invertebrates, the Emerald Crab does not tolerate copper-based medications or fluctuating water parameters.

Approximate Purchase Size: 1/2" to 1-1/2"

Customer Testimonials

Alex B Missoula , MT
Our emerald crab is great scuttling around and through the live rock in our 50 gallon aquarium. He's always picking pieces of algae off our rocks in and around our corals. He needs places to hide and often sticks one big claw out as a warning to keep our yellow tang at bay when he curiously approaches.
Kaylee S Charlotte , NC
These crabs do well in aquariums. Once, I put my finger on the tank. The crab would take either of its pinchers and touch the glass where my finger was! Talk about tricks!
Nick L Stone Mountain , GA
This is a great addition to a tank. It keeps my live rock clean. I would not put them in with large fish like sharks or anything. But that's common sense.
C Mills City Not Selected , LA
I don't have algae any longer so I give mine small nori pieces using my tweezers. I feed our Sally light foot crab the same way. Great that I can feed them this way "by hand"! These guys are pretty reclusive but get the job done and come out to grab what I have for them. I would recommend them.
Burnie B Meridian , MS
I have two Emerald Crabs and they are great on all my live rock. Beware, though, if you have a lot of caves in your rock work. I lost 3 smaller fish that liked to hide in the caves. One of my crabs got about 3" in size and had no problem grabbing the fish and eating them. I ended up giving it to a local dealer. The other is about 1" and is content grazing the rockwork.
Josh C Gurley , AL
Keeps the substrate clean. I had a lot of un-eaten pellets on the substrate prior to purchasing the crab and over night this crab, with help of my cleaner shrimp, had it all cleaned up.
Eric P Kempner , TX
Purchased this specimen due to a bubble algae breakout. Within two days all of the bubble algae was gone and has not returned after several weeks of ownership. Assists cleanup crew with algae removal during the night hours.
D Sprague Sullivan , OH
Bought 3 of these to try them out on an algae problem in a 28 gallon nano Cube. Temp acclimated them and dropped em in. As soon as they hit the bottom they went to work on cyano and later they were munching away at green hair algae. Hopefully they continue. I will supplement with nori or something once the algae is gone or move them to one of my other tanks.
Winston B Tallahassee , FL
We purchased two beautiful Emerald crabs from Liveaquaria but they have turned out to be too aggressive for our 26 gallon Cobalt C-vue. We have lost peppermint shrimp and hermit crabs to our Emeralds. They have been relocated to a fish only live rock tank where they cannot eat their tank mates.
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