10g is only enough room for 1 school of fish and a centerpiece type fish. I suggest choosing the Cardinals over the Rummies, as Rummies get around 2 inches and are pretty active tetras. 10g is not enough room for them IMO. Mine use up every inch of my 55g and school constantly. I'd go with 6-8 Cardinals and a Betta or Honey gourami. Its best to keep 10g tanks understocked if you can because of the small volume of water.