Both of those fish are characins from the Ctenoluciidae family. They are peaceful but predatory topwater fish that normally cohabitate with well with other peaceful, predatory fish.
A chief concern is that they're not aggressive feeders and will be out competed easily by most other fish such as cichlids and silver dollars.
All of these fish will grow to large to live for life in a 55. You'll need at least a 125 but a 180 or larger would be best.