Snails are hopeless.
Ramshorns are excellent for keeping a tank free of algae. Hoa I think that Neale Monks meant that snails were hopeless when it came to dealing with hair algae, such as Cladophora. Snails are good for the soft attached types, and can even chip away at green spot algae, but they can't eat the tough hair algae types. Well, I don't know about all kinds of snails, but I know for sure that ranshorns can't touch Cladophora and its kin. In much cooler Mississippi.