that type of filter is really 3 filters in one (if yours has a sponge - does it? if not, you might want to get a sponge filter to go with your filter or a thin sponge to slide into your filter). Your mechanical filter is the pad (catches the debris), your biological filter is your sponge (where the good bacteria grow) and your chemical filter is the carbon (which soaks in water toxins, but releases them back into the water when used up).
sometimes the carbon can make the filter look dirtier than it is and unless you're using the marineland black diamond
AC, i'd replace the carbon every week or 2 at least.
some good bacteria is in the pad, on the decorations and even a little in the water, but the substrata (gravel) and filter sponges are the favored homes of the good bacteria colonies.
you could try something like AccuClear for clearing up the water, along with frequent partial water changes until the water clears.
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), but I am surprised one rinse was not enough and it is still dirty. 
We had no idea she was even female, and have been in another room all night, only to come out and see tiny ginger molly shaped babies swimming around.
