HCA: Hermit Crab Association

I finished moving into my new 65 gallon tank last week and took advantage of the warm weather yesterday to pick up two new crabs to occupy it. My jumbo, Roscoe had spent all yesterday and last night in the moss pit while the newbies (having been dipped in the water dish to smell right) explored. Today I came back to find Roscoe standing on one of the newbies, a small, and once he had left I spotted the newbie's small claw and left leg nearby. The newbie is mobile, so I may leave him in in the hopes he gets more established, but I'm at a loss as to the cause of the aggression. They are nowhere near each other in size and there's plenty of protein in their diet. The only thing I can think of, aside from the newness is that the newbie was standing in one of Roscoe's favorite spots.

Since I just finished the move, I still have the old tank ready to serve as an iso if needed. Should I evacuate the newbie? Is there any way to better introduce them? and finally, should I place the severed limbs near the newbie as a gory-but-effective source of calcium and protein or keep them out of the tank to remove temptation for Roscoe?

EDIT: Newbie is now naked and in iso surrounded by appropriately-sized shells and easily-accessible food and water. Godspeed little buddy.

EDIT mk II: Newbie is clothed.

I would ISO the newbie, just in case its not Roscoe, but rather its ill/weak, and Roscoe is simply preying on it... ISO will allow him a better chance to recover IMO.

Oh no! I don’t have any advice but hope your lil guy recovers well. Sounds like you’ve got it well in hand, lucky for the new guy! I hope that’s the last you have to worry about that, and he recovers and grows them back successfully ASAP!


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Any news? How’s the little one doing now?


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I am not a hermit crab parent yet, but I have done a lot of research. If I were you, my guess would probably be to isolate him until he recovers or gets bigger and maybe get him a friend. Also if you do do that dip the crabs every so often in each other’s water dish so they will get familiar with each other, and when it is recovered/big I would put it back in the tank and try again. If it doesn’t work pls don’t get mad at me because I have not had experience yet. Hope this helps!

Okay...so a few things come to mind. First of all. It is recommended that jumbos be in tanks 75 gallons or bigger. I just wanted to mention that. I know you have been on the HCA a long time - Is your crab indeed a jumbo?

Do you have enough shells, and are they the correct type of shells? Is is possible that your crab was trying to pull out the other crab to try on his shell due to shell aggression?

Yes, I would definitely isolate the little guy!