This little ramshorn snail is in my aquarium. I have recently had a small population boomlet. I increased the lighting in order to feed my other snails, nerites. The nerites are either old, or too good at cleaning that there is insufficient food, for they are dying. If they increase in lighting does not keep they few left happy, then it was old age. Some food must be growing, because the ramshorn snails responded by reproducing shortly after I increased the light. To capture this image I had my Nikkor 60mm AF at closest focus on the Nikon D90.