I dont have any personal experience with peacock mantis shrimp, but for what I have read the consensus seems to be that a 30 gallon breeder is a suitable home for an adult specimen. Your tank may not be good for a peacock, but there are other smaller mantis that would be ok in it. Check out this link.
They live in burrows and caves and are absolute hunters. Just watch ALL the vids on them, they need a big enough tank to have multiple places to hunt from and bring their food into when they grab it. They also get pretty big 1'X1'X1' I would say is not near enough tank for one.
I had regular shrimp and crabs in my tanks before, from china town... Yep that's right .. China town, and they were thriving for months easily 4 months, until people scared me. But never had a problem with any of them, great scavengers.