Gorilla Crab in Your Tank? Why It Might Be a Hidden Treasure

The gorilla crab is an uninvited visitor to many aquariums that aquarists encounter. This crab is a nuisance and considered a pest of the corals, as they destroy corals and live rocks with their strong claws.

If you’re reading this, you’ve found a gorilla crab in your aquarium and don’t know what to do. You may also wish to pet the crabs or learn more about them so that you can be cautious in the future. Keep reading this article; you’ll know everything about the gorilla crab.

Quick overview of gorilla crabs

Common names	Gorilla crab, Furry coral crab. Hairy brown crab, Mud crab, Pebble crab, Rubble crab
Scientific name	Xanthidae (family)
Temperature	23°C–29°C (73°F–85°F)
Social	No
Sleeping nature	Nocturnal
Max Size	Up to 4 inches with legs
Lifespan	Up to 3 years
Color	Brown, Red
Diet	Omnivore
Reef safe	No
Temperament	Semiaggressive/aggressive

Gorilla crab facts

What is a gorilla crab?

The common term gorilla crab is used for a lot of species that fall under the family Xanthidae. Generally, they are hitchhiker crabs that come with live rocks or corals that cause nothing but harm to the aquarium.

The Xanthidae family has hundreds of species in 170 genera across the globe. So there is no specific identification of species for gorilla crabs. However, not all of the species from the xanthidae family are pests; there are many good species like the pom pom crab and genera like Tetralia, which has a symbiotic relationship with corals.

Note 1: The reason for your coral disappearing may not be the gorilla/xanthidae crabs; check for other reasons.

Note 2: Someone on the internet (I can’t recall) claimed the species of gorilla crab is Pilumnus vespertilio.

Where do gorilla crabs live?

Gorilla crabs make their homes in warm coral reefs and rocky shores, tucking themselves into little cracks and crevices. Sometimes, they sneak into home aquariums by hitching a ride on live rock or corals.

How to identify gorilla crabs

Before removing a gorilla crab from your aquarium, it is important to know what they look like, as you might accidentally remove a harmless species that could be beneficial or a new addition to your collection.

Appearance of rubble crab (xanthidae)

The gorilla crab has a rounded, hairy (Setae) body, including their legs and claws; the legs and claws kind of resemble gorillas, which is where their name comes from. Their color is usually brown to reddish brown and they have black tips on their pointy pinchers. Eyes can vary from blue, whitish, and dark to red.

They grow rapidly, devouring the surroundings, and can grow up to 4 inches with their legs.

Mostly their color resembles the color of the rock where they live, which helps them to camouflage; that’s why you might have a hard time finding them even though they were in front of you. 

Behavior of rubble crab (xanthidae)

Gorilla/xanthidae crabs are peaceful and cute when they are young and do not harm the corals; their movement is interesting as well as eye-pleasing to watch. That’s why most of the aquarists don’t have the heart to kill them.

They become aggressive and destructive as they grow, like destroying corals, eating fish, or any other anemones and invertebrates. Another intriguing thing is that gorilla crabs lose their hair as they grow.

Once they choose a spot, they make it permanent; as they grow, they’ll make the hole big enough to fit them by scraping the live rock or coral.

Gorilla crab vs. Emerald crab

The pincher of the emerald crab is more rounded, has no hair on the body, is green and does not pose any harm to the corals. On the other hand, the pincher of the gorilla crab is kind of pointy and they have hair all over the body, which is wider but not bigger than that of the emerald crab.

Are gorilla crabs reef safe?

Gorilla/xanthidae crabs are not reef crabs when they are adults. However, the younger ones rarely harm the corals or any other species. So keeping a gorilla crab in a reef tank is not recommended.

Note 3: Gorilla crabs are mostly interested in Acropora corals. 

Do they have any positive sides?

Certainly they have. It turns out that Joseph Pollock, a researcher, discovered something surprising about those pesky coral-eating crabs. While they can be a nightmare in our small aquariums, causing all sorts of problems, they actually play a helpful role on big coral reefs. These crabs munch on the dying or diseased parts of coral, almost like cleaning up the mess, which helps protect the rest of the coral. So, even though they’re troublemakers in our tanks, out in the wild, they’re like little reef doctors, doing more good than we might have thought.

Read related articles: 

• Magical blood of horseshoe crab
• Red emerald crab
• Another hitchhiker gall crab.
• Teddy bear crab

Are xanthid/gorilla crabs poisonous?

Yes, gorilla crabs are poisonous, and it will be stupid if you try to eat one, as cooking can’t destroy their toxin. However, they are not venomous and are safe to touch. Their toxin, which is similar to the neurotoxins of pufferfish, it is so deadly that it can lead to death and still now there is no antidote invented. The poisons are produced by the bacteria from the genus vibro which live in symbiosis with the crab. 

How to get rid of gorilla crabs / gorilla crab trap

Gorilla crabs typically move very slowly, but when you attempt to catch them, they become surprisingly fast, which makes it difficult to capture them. Here are some effective methods of catching them:

• I think using a fish net or a cup is the most effortless way to catch them. The gorilla crabs are nocturnal, meaning they’ll come out at night when lights are off. So make sure the lights are off and use a blue or red light while you catch them.
• To use a popular trap found on the internet, take a plastic bottle and cut it in half. Now invert the funnel part into the lower part of the bottle. Place some brine shrimp or any other food as bait, and place the trap near the crab’s hideout. If the crab goes into the bottle, it won’t be able to come out.
• Found an effective method on the internet: grab a whiskey glass or any small container about 3 inches deep. You’ll also need a frag plug (a small object to attach bait), a rubber band, and some shrimp from the store. Set the glass at an angle against a rock near the crab’s hiding spot, keeping it mostly upright. Take a small piece of shrimp, attach it to the frag plug with the rubber band, and place it at the bottom of the glass. The crab will go in for the food but won’t be able to climb back out. Do this at night when the tank lights are off. Replace the shrimp daily to keep it from rotting and adding too many nutrients to the water. It should only take a night or two to catch the crab. You can take it out of the tank and decide what to do with it once it’s in the glass. This method has worked for catching many crabs.
• Catch it with tools like tongs or spears.
• If nothing is working or you are not sure if there are any gorilla crabs in the coral, Just remove the infested coral and dip it into tap water. Immediately, the crab will come out.

Note 4: If you have encountered one gorilla crab, there is a high chance there will be another crab. So make sure no crab is left.

Note 5: You can prevent the whole mess by dipping new live rocks or corals into the solution first. Gorilla crabs can survive even when the rocks are dry.

Tip: Mantis shrimp eats gorilla crab

Tip 2: If you don’t have the crabs but you want them, you can easily find them in online stores.

What should you do after removing the crab from the main tank? Most aquarists say to keep them in the sump if you have one; they eat algae and live off it. My suggestion is to give food once in a while. In case you want to make a separate setup and care for the gorilla crabs, here is the guide for you.

Gorilla crab care

Tank setup for your gluttony (gorilla crab)

• Size: You can keep only one species in a tank (no tankmates). Choose a nano tank (5 to 10 gallons) with a lid.
• Substrate: Use sand substrate as usual; substrate doesn’t need to be thick as they don’t burrow.
• Other equipment: filter, thermometer, etc. 
• Water parameter: temperature: 23°C-29°C, dkh: 8-12, pH: 8.1-8.4, sg: 1.023–1.025.
• Corals: Provide them their favorite coral, acropora. If you can’t afford coral or live rock, place normal aquarium rock; there should be no problem.

What do gorilla crabs eat?

Gorilla crabs will eat everything, as they are omnivorous; they have records of living several months without food, only depending on the algae and debris in the tank. 

Consider giving them fish flakes and crustaceans’ food, raw meat, vegetables, fruits, brine shrimp and bloodworms.

Frequently asked questions

What eats gorilla crabs?

Predators like mantis shrimp, triggerfish, pufferfish, and larger wrasses are known to eat gorilla crabs. Some aquarists even use mantis shrimp to control them in reef tanks.

Are hairy crabs reef safe?

Most hairy crabs, especially those called “gorilla crabs” from the Xanthidae family, are not reef safe. While they may seem harmless at first, they often damage corals, eat small fish, and uproot live rock as they grow.

Gorilla crab baby

Baby gorilla crabs are tiny hitchhikers that sneak in on live rock or coral. They start off shy and harmless, but as they grow, they develop strong claws and a bigger appetite—so many reef keepers remove them early.