Probably could do a puffer. Maybe something like a Congo or Mekong. They are pretty sedentary and are not super active but would take care of your 'extra' live bearers. Ive never raised them so I might be wrong, maybe a puffer person could post.
Cool, thanks for clarifying. Any advice on how many to stock? I have ready they are aggressive toward each other but some suggest this is only in larger spaces? Got to love the interwebs and the conflicting info!