if its teh 125 ur talkin about then i wouldnt see why not and ya u can add sum congo tetras try 12 to 15 they look awsome in big schoolings but they may get picked on by the breeding HRPs. if u do add the angels get 3 to 6 if u want to see schooling ( see them school at the LFS and they had a 300 with 15 angels schooling ) but just get 3 to 6 if u want or can.