I personally like American, but if you want a larger stocking volume, Africans will be the choice. Depending on species you could probably due 10-15 Africans in a 75, but would really be pushing more the 3 or 4 Americans, and even that is only if you go with some smaller species like Firemouths or Rainbows. If you want something bigger like an Oscar or Jack, you would probably be limited to the 1 fish, and maybe a second, but unlikely.