Dont mean to hijack my own thread, but what is suitable with them?
It's a gamble...
When you talk about mantis shrimps and state things that can and cannot live peacefully with them there can be a lot of bad feed back xD so everything I state is from my personal experiences with the mantis shrimps I have personally kept.
From my experiences mantis shrimps are extremely misunderstood... a happy mantis is a safe mantis and a happy mantis is a FAT mantis :p what I mean by this is you personally feed it! What this will do initially is start a bond between you and Mr./Mrs. Mantis once he/she understands you are the 'be all and end all' of easy food sources Mr./Mrs. Mantis will start to become more inter-active, by feeding your mantis directly and not making it hunt for food on its own you lower the risk of it killing things greatly.
A mantis shrimp will not kill for the sake of killing...animals like to save there stored energy for life threatening times albeit if he/she is STARVING or if he/she feels threatened (they have the energy ready) why waste it ?
Also I said when you start to feed your mantis directly they will become more inter-active because they learn fast...like REALLY fast, so Mr./Mrs. Mantis will assume that whenever your comming to the tank its feeding time and he/she will shoot out of the rocks wagging his/her tail as if she/he was a little poochy! :p
By doing all of this you keep your mantis happy and it learns that there is easy food so it won't actively hunt.
having said all the above....mantis shrimps won't just let another creature "walk over them".... my foolish boisterous blenny learnt the hard way :D the blenny dwarfed the mantis shrimp (Rocky the small male G.graphurus). Well somehow Sun (the blenny) got into Rocky's enclosure...at first I was concerned for Rocky cause Sun could of gobbled him up! I mean Sun's mouth is big enough too! Well within the container to make Rocky feel comfortable I have a piece of PVC pipe that he resides in.
Sun wanted in...she got half way in then I heard what I expected, WACK! WACK WACK! Sun retreated so fast that she got wedged inbetween the lid of the container and was stuck so I had to help her get "unstuck" I'm sure she learnt a hard lesson :D
I said it at the start and I say it again.
It's a gamble....
Hope this helps a bit ;)