What cool fish should i add?

[Orhan K]

Hi i ahd 5 platys and 4 rummy nose tetras but had to take out 2 female platys because of the male who was being really aggressive and then he killed my other male.

so now i have 2 platys 1 male and 1 female who get along fine
and 4 rummy nose tetras in a 15 GALLON TANK what fish should i add i was thinking of 5 - 6 black skirth tetras
sorry it says BLACK SKIRT TETRAS