I already have one frag on a rather large rock and want to add 1 or 2 other types and have it grow in together to cover the whole rock I just wanted to make sure one would kill the other and just take over the rock
I would frag the ones you want to mix up and glue them to a separate rock for a little test to see if there is any problems between them, most times it is ok, but sometimes one is a really dominant species over another. That way you won't lose your whole piece of anything if there is fighting between them. And, in a short time you'll have what you want on the new rock. That is what I would do, and probably should do, I have a bunch of Monti's I could mix and match. Good luck, I hope it works out for you.