pest snails

These snails are everywhere in my tank in all kinds of sizes and appear to only be active at night. Are they coral pests or beneficial hitch hikers?

Is this a sundial? The shell is not flat like pics of sundial snails. It’s shaped like my nerite snails in freshwater.

I've had a sudden explosion of these little guys (snails of some kind) in my frag/grow out tank. They have a similar shape to a conch shell, but the biggest I've seen as been maybe a centimeter in length, max. I can't find anything on the web about them either?! They seem to reproduce fairly...