Siamese flying foxes seem to be the best, and red-tailed sharks pretty indifferent. Plecs are more variable. Whiptails, Otocinclus and Twig catfish make almost o impact at all. Panaques are vegetarian, and happily eat the leaves as well as the algae. All of the Loricariids make good all round scavengers, but don't expect too much.
Snails are hopeless.
Mollies can be effective, but are picky feeders and will damage fine leaved plants. Similarly, Scats adore hair algae, but uproot the plants as well. Providing the plants are vigorous, the easiest thing is to remove the heavily overgrown leaves that have hair algae. Nothing else will destroy it. Green algae won't bother most plants, and makes excellent forage for cichlid and livebearer fry.