From that list I would say electric yellow labs are your best bet. A 50 gallon tank is only 3 feet long so I don't think the acei or electric blue haps would be happy in a tank that size. Red zebras can be hit or miss. Some do great others are psycho killers.
Avoid auratus, Kenyi and bumblebees. These are your super aggressive killer mbuna. Hopefully someone will mention a good online site you can get fish from. That way you'll have way more choices of suitable mbuna.
Avoid auratus, Kenyi and bumblebees. These are your super aggressive killer mbuna. Hopefully someone will mention a good online site you can get fish from. That way you'll have way more choices of suitable mbuna.