Okay. All of that makes sense, and I hadn't heard it before. In my Pleco post I did say I was looking for another home for him incase the girls wouldn't like him, or vis versa. So maybe I'll just keep looking. He's only about 3 inches right now, and that's a 10 gallon. So he should be cool for a little while longer. I guess I'll get a couple more tanks before I invest in Bettas.
Thanks so much! I'm even more glad I researched this before I just bought 8 betta girls!
PS - Also, sorry I forgot, how do I determin the least aggressive? Is that toward me? Or do I use a mirror, cause that seems kinda mean, but I don't know how to gauge it.