Tiny critter in aquarium

[julia1802]

Hi! I'm fairly new to aquariums and have had my 20L one for about a month. I have 4 mollies, two of which I added yesterday. Today I noticed this small critter (?), bug(?) or something crawling on the gravel and wanted to know what it was and if it is harmful to my fish. There are also some very small almost transparent dots stuck on the glass that I wonder if they may be eggs from this creature. I have some snails in the tank as well that I think came with my plants if that helps. I have pictures of the creature but couldn't get the eggs on camera. I would really appreciate if somebody could help me identify it so I know if I should do anything about it, thank you!!

[Sniperhank]

Looks like a really small stometella snail to me. Harmless member of your clean up crew.
They aren't flat though, right? It appears they are dome shaped to me.