For Aphids: "When ants aren't keeping them away, the best natural predators for aphids include ladybugs, ladybug larvae (which look like little alligators), birds, lacewings, lacewing larvae (called aphid lions), earwigs, hover (flower or syrphid) ßy larvae, soldier beetles, and parasitic wasps. If you order predators, lacewings are best..." --http://www.ucpress.edu/books/pages/8778/aphids.html For Fungus Gnats, Shore Flies, Moth Flies and March Flies: "Predators, such as rove beetles (family Staphylinidae) and ground beetles (family Carabidae), help control fly larvae outdoors in areas not sprayed with broad-spectrum insecticides. Commercially available Steinernema nematodes, Hypoaspis mites, or the biological insecticide Bacillus thuringiensis subspecies israelensis (Bti) can be applied to control fungus gnat larvae in container media. Nematodes can provide relatively long-term control of fungus gnat larvae and they can be self-reproducing after several initial applications to establish their populations. Steinernema feltiae is apparently more effective against fungus gnats than other commercially available nematode species. Bti does not reproduce or persist; infestations in media may require repeated applications at about 5-day intervals to provide control. Mix Bti or nematodes with water and apply as a soil drench or spray onto media using conventional spray equipment..." --http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7448.html