If u have 12 they should be solely focused on each other. I only have 5 and all they do is chase each other 24/7. Never bother my gouramis. If u had only one then it would definitely be a problem.
I have mine with Geophagus brasiliensis, a Gymnogeophagus balzanii and a EB Acara, but there'ss other dithers besides the Tiger barbs (danios, mollies, platys, guppies,etc.) and bottoms feeders