Snails can be messy, so they may clean some algae, but pollute your tank with their poo at the same time. If it's just algae you want to battle, I would just manually clean it, but if you really want snails, then you have to consider that they take some care as well. Also if you get a couple of snails, be prepared for them to breed. I have hundreds of Ramshorns now, and I only started with two
It might be safer and healthier for your fry if you just manually clean the algae, but it's up to you.
Does the snails you saw look like this?: