20, 3-4cm females as adults in a 60l, before we even talk about stored sperm packages that could give you births for months... which already has "a few corys" in it (hopefully Panda; Pygmeus; Hastatus; Habrosus)?
So, when is this setup getting an upgrade to at least a 240l? On what you have written so far, this sounds that a really badly thought through idea...