I have a pair of Butterfly Rams and they don't bother anything. They mind their own business. Not had them for a great deal of time but so far they seem absolutely fine.
My Rams were the last to go in bar 5 dwarf gouramies and they haven't to my knowledge bothered a soul. The male occasionally butts the female for no apparant reason but she just kind of side steps him and doesn't seem to fussed. The Rams are fun to watch though, one of my best buys.