Can you ID these critters?

[TWYOUNG]

I've been finding quite a few of these tiny, < 1/4", critters primarily in my skimmer and a few elsewhere in the sump. They hold on VERY tightly, thus their ability to hang on in the skimmer, and pretty much have to be scraped off.

 

[DaJMasta]

Limpets, a lot of small ones mean they probably spawned in your system.

While predatory ones exist, the majority, especially if spawning in your system, eat algae like other snails.

 

[56longroof]

There is a smaller species of limpet. My sump is full of them.