What Fish

WE need a bit more info then that. since this is the cichlid forum are you asking what sort of cichlid would work? What size tank? any other tankmates? water parameters?

First, you should be doing daily partial water changes to keep the ammonia down during the cycle. If this tank is newly set up, please tell us how long it has been up and running.

Also, are you specifically asking what cichlids would do well mollies, or are you just looking for any type of compatible fish? If the latter, I will move this thread over to where you will get more responses.

Finally, mollies like a little salt in their water, and are fish that are not really compatible with a lot of species. They are in fact harder to keep than they seem. You would want a small cichlid that can handle brackish conditions and does not grow too large... the one that comes to mind is the Orange Chromide. Even then, given the relatively small size of your tank, probably only one or perhaps two would fit.