Drop the mollies. They would not go well in an aggressive tank full of tiger barbs, dwarf gouramis and the shark. Those fish may be fine with each other but not with mollies. I love my livebearers but recognize that they do not do well with all other fish. The plec would probably be OK in there and the genetically modified zebra danios, glo-fish, would probably be quick enough to stay out of trouble in there.