Ostarcods- These are small bean shaped organisms. They are entirely harmless. They may be brought in with live foods, plants, or even through water supply. They live in an opaque shell that may be whitish yellow to brown or sometimes green in color. They are 1-3 mm long. The most obvious protrusions from the shell are two antennae and a pair of slender legs, which are withdrawn rapidly if danger threatens. They feed mainly on decaying matter. They provide a someone useful function. Some fish will eat them, and unless they become an unsightly problem, there is not a need to remove them!
thats the best info i could find given the info you provided, are they just on the glass free swiming on plants and stone too???
how long has the tank been set up and whats in it?