Supposedly assassin snails never go after one another.
I have had them in a few of my tanks for the last few months, so far they have killed off a ramshorn issue in my shrimp tank. Now they are split (I have 7, maybe 6
, total) between 2 tanks. They don’t do as great of a job killing the ramshorn being split into two smaller groups. Although one pair has been mating, so once the eggs hatch (if they do) I’ll have that issue taken care of.
I personally think they are a great way to take care of a pest snail issue. And once they are finished killing off the snails (if they can keep up with the breeding) they do feed on other sources of protein. I have personally seen mine eating frozen bloodworms. And that was while there were still ramshorn in the tank.