I do have shrimp tank and have also problem with seed shrimp plague, They are not completely harmless, they are eating delicate plants like water sprite,, even water liily..I've got 1 platy to get rid of it ,and platy ignores seed shrimp, they have hard shells and most of fish wont eat them. the good thing is platy doesn't bother cherry shrimp, even the babies are ok, swimming all over the tank. still the problem exists. I've heard tetras like black skirt or gouramis would eat them, but I wouldn't take a risk, if You have shrimp like me in the tank, smaller fish wont eat it for sure