ID this little crab hitchhiker please

chrislynn · Mar 23, 2021

Type of crab? Came with my new polyp colony.
tha is!

Dolphins18 · Mar 23, 2021

If its hairy it could be a gorilla. Unfortunately crabs aren't something often worth taking a chance with. Maybe you have a sump if you'd like to keep him, otherwise it may be best to remove it for good.

chrislynn · Mar 23, 2021

mstoneman17 said:
If its hairy it could be a gorilla. Unfortunately crabs aren't something often worth taking a chance with. Maybe you have a sump if you'd like to keep him, otherwise it may be best to remove it for good.

Thanks! I did a Google on gorilla crab and it doesn’t look like those pics based on color and non-hairiness in person to me.

duberii · Mar 23, 2021

Maybe a sally light foot?

Joe's 220 Reef · Mar 23, 2021

duberii said:
Maybe a sally light foot?

Pictures are not great but that is what I thought from the first picture as well

r20crazy · Mar 23, 2021

crabs with black claws are bad.

chrislynn · Mar 23, 2021

Joe's 220 Reef said:
Pictures are not great but that is what I thought from the first picture as well

Thanks! I’ll have to try and get a better picture! He’s little and blue with striped legs.

vetteguy53081 · Mar 23, 2021

very much like sally lightfoot. Cant see face or front claws.

vetteguy53081 · Mar 23, 2021

Hmmm- does it look like this?

chrislynn · Mar 23, 2021

vetteguy53081 said:
Hmmm- does it look like this?

Closest to this so far, but blue.
what’s this?

vetteguy53081 · Mar 23, 2021

chrislynn said:
Closest to this so far, but blue.
what’s this?

Its a crab from the family Xanthidae. They’re also known as mud crabs and some of them are brightly colored, although the ones that pop up in the aquarium are usually more of a muddy color. They are also named: Gorilla crabs which are often confused with emerald crabs, which do also occasionally hitchhike into the aquarium. You can tell the difference by looking at the claws: many gorilla crab species have distinctive black claw tips that are not really seen on other aquarium crab species. The emerald crab, for example, is fully green including the claw tips.
The gorilla crab grows a lot larger than most beneficial crabs. Mature specimens will develop a “hairy” appearance on their claws and even their carapace, which is probably what lent them their common name.
There are various crab species that can come with your live rock or even hitch a ride on corals. Some are pretty neat, like coral crabs from the genus Tetralia which actually maintain a symbiotic relationship with corals by cleaning them.
And then there’s Xanthid gorilla crabs, whose only goal in life appears to be to wreak havoc in our reef aquariums. They grow quite large and are omnivores that will eat literally anything that they can get their claws on.
Corals, invertebrates like shrimp, starfish, anemones, clams, even small and slow fish won’t be safe with a gorilla crab around!

fragglerocks · Mar 23, 2021

great write up!! very useful information ^

would also like to say, and don’t quote me on this....
but i believe that might be a commensal crab.
the coloration seems to match its adopted host

chrislynn · Mar 23, 2021

vetteguy53081 said:
Its a crab from the family Xanthidae. They’re also known as mud crabs and some of them are brightly colored, although the ones that pop up in the aquarium are usually more of a muddy color. They are also named: Gorilla crabs which are often confused with emerald crabs, which do also occasionally hitchhike into the aquarium. You can tell the difference by looking at the claws: many gorilla crab species have distinctive black claw tips that are not really seen on other aquarium crab species. The emerald crab, for example, is fully green including the claw tips.
The gorilla crab grows a lot larger than most beneficial crabs. Mature specimens will develop a “hairy” appearance on their claws and even their carapace, which is probably what lent them their common name.
There are various crab species that can come with your live rock or even hitch a ride on corals. Some are pretty neat, like coral crabs from the genus Tetralia which actually maintain a symbiotic relationship with corals by cleaning them.
And then there’s Xanthid gorilla crabs, whose only goal in life appears to be to wreak havoc in our reef aquariums. They grow quite large and are omnivores that will eat literally anything that they can get their claws on.
Corals, invertebrates like shrimp, starfish, anemones, clams, even small and slow fish won’t be safe with a gorilla crab around!

Got it! So how do I evict him from my tank?!
Thanks so much for the amazing info!