tiny white snails

Hard to say, not knowing what kind they are. Many snails show up in tanks. There are some tiny, nasty types like pyramidellids, that stay small. Strombus maculatus gets somewhat larger and it just a grazer. What do they look like?
 
hmnmm, seems not much can be said of them. They are pure white. Conical shape like Cerith or Nassarius. Move around well. Noticed them first about 6 months ago. they do not seem to grow if any. But I have hundreds. Don't seem to do any harm to anything. Just seem to be grazing the rocks but they are also very abundant in the shade.
 
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