It depends on your tank size what you can add. Most of the tetras, variatus, platies, guppies, etc. do very well in a tank with mollies. I recommend looking at the website Aqadvisor, you can put in your tank size, filtration, and current stocking and then look through some other fish that work for your tank size. It will even tell you how much water to change every week.
I'm mote of a reptile guy, but my father had a large tank when I was younger. He loved Molly's and he also had neon tetras with them and even angel fish. Hope that helps.
Not sure but they will be able to tell you.
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