Invertebrate Identification?

[Woodlol]

I've got these funny little fellows in my 10gal... I thought for a while they were baby snails as my big pond snail Frankie has been laying like crazy but they don't seen to get any bigger... They look more like barnacles than anything else. Any ideas? The last picture you can see an ACTUAL baby snail next to one of them.

 

[Essjay]

Fresh water limpets. I have them in my shrimp tank.

Acroloxidae
Common names: freshwater limpets

From https://www.fishforums.net/threads/snail-species.75554/ :
"They are both really small snails and their hood-shaped and limpet like shells don't have whorls. They aren't really limpets, but they resemble them (...). They breathe through skin and lung. They don't fill their lung with air like most of the other pulmonate snails, but they keep it filled with water. The walls of the lung sack have lots of blood vessels, that makes it easy to exchange oxygen and carbon dioxide through the walls. When the snail has used up the oxygen from the water (or air) and it is filled with carbon dioxide, the snail will release the old water and take in new.

They usually won't do much damage to plants since they are really small, but they can look really ugly if there's too many of them. If you look closely, through magnifying class, you might find these little hermaphroditic (snail has both sexes, but usually need other snails to fertilize the eggs) snails interesting.”

 

[Colin_T]

Freshwater limpets. Harmless curiosity that eat algae and uneaten food. They are fine, leave them alone