I have these things in my tank the size of about 5 mm really tiny you see them all over the walls of the tank are these like fleas or something bad or did my snails have a whole lot of babies?
I am guessing they are "pods" just google copepod or amphipod and see if there are the same thing, if they are pods no worries, they are a good thing/source of food for your tank's inhabitants.
99% are good, there are some bad ones, but I have never seen them imported into the hobby. The likelyhood of you getting "bad" pods is incredibly small.