On the rotifers being microscopic I would like to ask why you say they are microscopic? Wickapedia and other sites say they are microscopic and up to 2MM.
"phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Anton van Leeuwenhoek in 1703.[1] Most rotifers are around 0.1–0.5 mm long (although their size can range from 50 μm to over 2 millimeters)"