Exactly, Vermetids, a type of filtrator sesil snail. Bad or good depends of the number of them. Are commun in aquariums and the number of them increasing by organic particles in suspension. So be carefull with animal feeding and mechanical filtration.
A handful of bumblebee snails cleared them from my tank. I haven’t seen a single one in about 9 months. Of course the number of bumblebee snails depends on the size of your tank.