Friends, not FOOD!

[mistercrabbypants]

I feel like I'm going crazy here. I need a reality check, or help please!

I (used to) have a stable group of crabbies (4 total) for the past 10 years. Things were going well, until something happened recently. They all molted at the same time, and 2 came up with missing limbs, and 1 never came up at all. The 2 with missing limbs were being picked on by the one "survivor", so I isolated (same tank, just used a barrier to keep things civil) until the 2 "disabled" crabs were healed and acting normally. This went on for so long that one of them was able to molt again and regrow his missing limbs.

ANYWAY, the very night I reintroduced all 3, the "survivor" went on a spree and devoured the others. He was alone now. I reevaluated my entire setup, changed a couple things, and after a bit of time, thought he could use some company again. I found 2 new crabs from the same colony that were somewhat close in size to my "survivor". I did slow introduction, and monitored them closely. They were fine for 4 months. The new ones even molted unbothered! But once again, one random night, my "Final Guy" decided he wanted to eat his friends.

It's been 2 months he's been alone. I know he isn't happy being alone. But why does he keep attacking his roomies? Should I try to add more friends or give up and find someone that can kick the "cannibal" out of Hannibal?

Some info: I have a 45 gallon tank, use eco earth (about 5-6 inches deep). I feed a variety of fresh fruits, dried leaves, and offer protein and calcium regularly. They have both fresh and salt water "pools". Food is changed daily and water is changed about every 4-7 days. I switch out climbing toys at least every 8-10 weeks (not a full change, just substituting 1 toy for another occasionally).

[curlysister]

Sometimes crabs simply can not live with other crabs. If he keeps killing his tank mates, I wouldn't get him any more. He won't be lonely. He can continue to live solo.
I don't know why this would happen after all this time. Altho 45 gallons might be a bit small for crabs that are probably jumbo by now.