Help! Infestation of..... I don't know?

[Catnkit]

Hey all, I have recently gotten some sort of infestation in my tanks (first one, now two). They appear to be tiny translucent dome-like creatures with a dark spot in the middle, they have a thin shell which makes an audible (if tiny) crunch when I crush them with my nail. They're really tiny, ranging from pin-head size to a mm in diametre. I've been seeing them on the glass, and just discovered they seem to like being on broad leafy plants too, I'm seeing holes/dark spots on the plants too but I don't know if they're to blame or my rc shrimp. I haven't seen any on my fish, but all the fish in that tank are very small themselves. The things seem to like being higher up when on the glass, all of them are within wrist-deep crushing range.

I can't get my camera to focus on them, but the clearish dome + dark spot midle is a pretty much all there is to them.

Are they snail babies? Fish fleas? Plant feas? I can't seem to google anything that looks like them.

Please help!

EDIT:

Holy jesus, the closer I look the more weirdness seems to be showing up ont he glass! I'm seeing tiny translucent round things jumping on the glass and little triops/'y'-shaped critters scurrying around, even quick-moving white/translucent leech-shaped things, all of them so tiny I would never have noticed if I wasn't looking so closely. What are all these things?!

 

[knifegill]

I know what they are, I just can't remember the name. It's not scallop, but some sort of mollusk you'd normally associate with saltwater. They're common and normally harmless.

Limpet! Freshwater limpet!!!

 

[Catnkit]

This is a freshwater aquarium, do they live in freshwater?



EDIT: After getting a burst of inspiration, I googled "tiny creatures living aquarium" and got a page with a bunch of common buggies normally found in aquariums. The disk-ones are "limpets" and the "y"-shaped ones are cyclops, worm(s?) probably a nematoid and the little oval things one of the other things on there.

ie, everything seems to be harmless (even if the limpets are butt-ugly on my glass), so I'm calling this topic closed, sorry for making a useless thread!

Thanks for replying knifegill!