Crab Identification

[CJ Amber]

I somehow got two hitchhikers. One of them was in my sump and the other was in my display tank. These crabs were eating everything, including my snails, hermits, and some of my fish. They have grown to about 2"-3".
Please help me ID these two crabs.
Thanks,
CJ

 

[sbash]

Could they be xanthid crabs? They are amazing looking... Probably bad for fish, but a great excuse to set up a fishless nano tank!

 

[ohdanny]

Dang, these guys are eating fishes too? LOL get rid of em!!

 

[CJ Amber]

Thank you! They are pretty cool looking. Yes, I did have a 28 G JBJ Nano I set up a couple of months ago with no inhabitants, so I dropped the light colored one in first since it was smaller, and then I'll drop the other one in maybe tomorrow morning.

It ate my 9" long Engineer Goby, a few of my large hermit crabs, a few of my large turbo snails, and I had to take a stand and remove them before they ate my Vlamingi and File fish

 

[Sully]

First one has black tips, never good.

 

[CJ Amber]

What do black tips usually signify? Both of them have a darker tip on their claws.

 

[Naiad]

The black claws are are a signature of the more predatory species of crabs in the xanthid group. Designed to slice flesh rather than pull algea.

 

[Sully]

What Naiad said.

 

[Salty1962]

When in doubt, throw in sump! They will eat everything they can catch, which is most everything!:mad: It took me weeks to figure out why my gobies were disappearing then one night found a gorilla crab in my dt, threw him in the sump and no more fish mysteriously disappearing.

 

[CJ Amber]

If I threw them in the sump, would there be enough junk or do I have to feed them? I know crabs are bottom feeders, but do they eat the excess crud/proteins left that the skimmer didn't catch? Would almost like to keep them alive

 

[Sully]

I have 3 smaller crabs in a HOB fuge (about 3.5 gallons) They have been doing fine for about 2 months. You can always throw a pellet in there every few days.

 

[CJ Amber]

Hmmm, that's a good thought. I may want to do that instead of putting them in a 28 G by themselves, then it's almost a wasted display tank

 

[Naiad]

They will do fine for a time. Throwing in a krill or something from time to time will ensure growth

 

[azbigjohn]

Wow, I am amazed if a 2" crab caught and ate a 9" Engineer Goby....

Definitely either a sump dweller, or a dinner plate dweller if they get bigger...

 

[CJ Amber]

The engineer goby was under the rocks, and I suspect the crab grabbed ahold for a fatal clasp, and then kept it under the rocks and ate away at it... it was a pretty tank mate!

 

[Salty1962]

Add little butter and garlic, hmm hmm good!