I think the mantis you are referring to is what they call a Lime Green mantis and sell for under $20. I'm pretty sure that it is not a peacock, but I could be wrong. I think they call any mantis they get in a lime green mantis and they always show the same pic, so it may not even look like the pic. If it's not a peacock, it probably won't get terribly large. You can probably keep it comfortably in a 10-20 gallon setup.