White barnacle type spot. Help what is this?

[Lgarden]

I have a small fresh water tank. I just got a new plant. I have two guppies and a snail. These white and beige coloured spots have appeared and I have no idea what they are.

 

[SaraB]

Do they move? They might be limpets or another small hitchhiker snail.

 

[Lgarden]

Do they move? They might be limpets or another small hitchhiker snail.

They don’t move around.

 

[libertybelle]

I can’t tell what I’m looking at in that pic. Is that the tim of the tank?