There are lots of FW
shrimp. It really depends on what you want them to do. There are some that specialize in algae and some that just roam around looking cool and eating this and that, like ghost shrimp.
I keep Amano shrimp and cherry shrimp and they do eat algae, but not to the point where they are "required" for keeping a tank clean. They have their own impact on the bioload (greater than you think!) and are often consumed by the tank inhabitants.
Snails will eat algae, but I find they basically leave trails in the algae, rather than removing it to the point where you don't have to scrub it. These are both cool animals that make our tanks more interesting, but I don't think they fulfill the same role that they do in a SW