Really tins didn't work that's supprising. Dats are a never fail and flagtails are great too but i'd say cichlids too like an oscar a jd or a gt or a jag it may not work but its worth a try and if not you cant go wrong with 2 aros or 2 gar depending on tank size
i have oscars their nice but really messy they let off alot of amonia to the tanks so dont go with these get a nice big red devil or a pacu you can deff put 2 in there