Algae (?) on Japanese Rush


Two of my Japanese Rush has some sort of growth (like fungus on stale 
bread) on 1-2 leaves . I can't seem to identify it to any algae from the 
Plant FAQ. The colour is clear/white and shape like below. It is about 
2mm high and grow on dying yellowish leaves. My Black Molly don't even 
eat it. Anybody guess what it is?


I don't know much about Japanese Rush. Can someone elaborate on its 
growth condition/requirements. Thanks.