Crab Id (Again)

Frigideus · Sunday at 9:52 PM

Asking about this crab again but only because he brought along his equally large red friend this time. These guys don't seem like they bug my fish but due to their size I am a little afraid they may turn on me someday. They also like to nip at certain corals but have left most of them alone. I need IDs and ideas for what I can do with them. I would love to put them in my sump but I have a slow moving sea hare and a juvenile Bangaii living in it and I don't know if they will get along.

super cool and love to fight with the cleaning stick but seems like they could become liabilities.

Reef Jedi · Sunday at 9:54 PM

The red one is an emerald crab. Good for eating algae. Not sure of the other one but since it has pointy tips I would get rid of it. You wouldn’t want it in the sump.

Edit: asking the new Siri (beta), it still put that other one in the gorilla crab family. I would still get rid of it due to the pointy claws. — I don’t normally ask ai but tried it based on your photo for beta testing.

vetteguy53081 · Sunday at 10:02 PM

Emeralds and male hard to trust as some will go after coral

Frigideus · Sunday at 10:12 PM

this is the closest thing i can find to how it looks. https://tbsaltwater.com/blogs/it-depends/tbd-crab it doesnt look anything like the gorilla crab. they also have one called the ruby clinging crab: https://tbsaltwater.com/blogs/it-depends/ruby-clinging-crab-mithraculus-forceps . my rock came from TBS so I can sort of assume these might be correct? They are both 'reef safe with caution' so I am not quite sure what to make of it but thankfully neither of them seem interested in attacking livestock. I just have nowhere to put them even if I were to pull them out so I am a bit troubled by doing so.

LiverockRocks · 2026-07-29T06:58:03-0400

Good morning,

Thank you for choosing TBS to harvest for your tank!

The first photo is for sure the - Shaggy Clinging Crab - beneficial algae eaters on ocean reefs. These guys have blunt, pink tipped claws and are excellent live rock cleaners. We haven’t found them to be troublemakers or harmful to fish. Easy to catch, so if you are worried, then add it to your sump or donate to a LFS.

The second photo is an adult - Ruby Crab beneficial algae eaters on ocean reefs. These crabs are EXCELLENT reef tank live rock cleaners as juveniles; however, when adults they are known to cause trouble by sampling corals. If you have sps or notice nibbling on softies. then sump or donate the ruby to a LFS.