Common pond snail (sometimes called a blister snail). My daughters like those I "inherited" with some plants... But they are capable if reproducing exponentially. I find them in my HOB filter on the filter pads... Usually still alive (after the journey through the tube and impeller!).
Some fish will eat them, particularly loaches. None of my fish care two beans about them. Assassin snails will eat them... But are slow about it (eat one, burry into substrate for a few days, out to hunt again, then burry up fir a few days).
If you overfeed, then you will encourage a population boom.