I'd like to distract them from each other. my sev is boss right now but as they grow out I kind of expect that to change. I have 12 zebra danios in the tank that they pay no attention to. The danios don't even feel the need to school. So I thought something smaller that will try to claim a territory and be seen as a threat. I've been told a convict or two of same sex could work. If they can why not a couple dollar sunfish? besides that they might be a little more aggressive, I don't see the downside compared to just getting a convict.
Dollar sunfish are native all the way down to the gulf, so (while not optimal) 78 isn't a bad temp in my eyes. As far as parameters go, regardless of what fish they were kept with they'd be in my tap water.
Now if I'm being told by everyone I don't need anything like that then I won't get them, you guys know better than I do, that's why I'm here. I have just yet to find a tetra, danio, barb, rainbowfish that I'm the least bit interested in getting.