the mollys need alot of algae in thier diet their diet consists of almost all algea. i suggest buying algae flakes or algae wafers(the kind you feed plecos). the molly has always been in my brackish tanks for a couple reasons(cheap fish to start a tank up and their babies provide a source of food for some brackish fish) most gobies diets consist of live food...worms,insects,and baby fish. make sure you have plenty of plants for the babies to hide in. plastic and grass matts(ive even used that plastic grass used in easter baskets floating on the top several inches thick for the babies to hide in). i would try feeding the violet/dragon goby chopped earthworm"make sure its still wriggling to intice its feeding response". the only live plant ive tried was the java fern. the java fern worked well for me and it is truely a brackish plant as long as its just slightly brackish(1 tablespoon / gal). that is the salt ratio i have used and did well with. i read tons of books and asked tons of fish store/keepers and that was the salinity i decided on. use the hydrometer too to keep the salinity in check(especially in the summer when you habve more evaporation) good luck the brackish tank does have interesting fish options. oh i have kept up to 3 bumble bee gobies in the same tank no problem they even bred for me . good luck