welcome to SW!!
you find out quickly that certain critters will only eat certain things. this is why an assortment of snails is recommended. each snail likes to eat a certain kind of algae. they are picky eaters. snails also only eat for a short period of time per day. they then sleep.
sounds like you are in the beginning of the tank cycle. you will get many of these different
algae blooms. these will last until the tank matures, at about the 1 year mark. this is not a hobby for the impatient.

this is why recommend to people to not put anything in the tank except for LR for the first 2 months. you will drive yourself crazy worrying about how to cure the algae blooms. just let them do their things.
G~