i think it is a good idea. people unfamiliar with the set up of the forum would now instantly know where to post questions on bw setups and fish. though i do foresee a great deal of moving threads by the mods until people realize they should post it in the bw forum.
i do think mollies, since they are sold as mostly fw these days, should continue to be discussed in livebearers.
as for bw puffers................. that could get a bit confusing for folks, especially those new to puffers who may not even know they are talking about a bw fish (again, i see the mods doing a lot of moving of posts for a time.....)
a bw forum would also help bring awareness of this awesome branch of fish keeping and will give those with knowledge and experience a better chance to share that with us all.