I was cleaning my tank when I saw little pieces of sand where clinging to the tank? Earlier there was this white film (I don't have a picture) laying on the sand but I wasn't thinking anything of it and sucked it up. It looked like a foggy piece of film. Then I saw that they were MOVING. They have a red bottom with a white head and are incredibly small. Are these harmful? What are they? Do I need to treat the tank? I drew on the picture that I took of them for a closer look as to what I see! Please help!