Eh, I don't think so. Even if your mantis leaves the eel alone, there is no way the eel won't try its hardest to eat the mantis once it gets bigger. If the peacock is smart it will kill the eel before it becomes a threat. Plus I doubt your mantis is in a tank anywhere near big enough for a snowflake. Just because it is 5" now doesn't mean that it won't grow up to be 2'.