ID Help snail/worm and sponge
 

Hello,

I have a few of these things on the rock. I see them at night. I once saw one on glass that looked like a seal. theres a dark center spot on these white circles. They are very small. maybe less than 1/8 inch. Are these dangerous and should I get rid of them?

Also I have these green sponge type materials Any idea on how to id these as well?

Thanks

I meant snail not seal. Couldn't edit post

the first is a limpet, pretty cool hiker as long as it's not a keyhole limpet (which it does not appear to be), the sponge is a sponge, species of poriferans are typically difficult to ID without a microscope and more knowledge than I posses but that yellow/green guy is pretty common in tanks and I love the look of them. but simply a beneficial filter feeder.

Don't think its a limpet, possibly a stomatella snail.

Either one is good for your tank.

Thank you!

I must respectfully disagree.
stomatella are shaped like a rounded fingernail, limpets are teepee shaped.
Stomatella
https://i.imgur.com/kY0EhYHm.png

Limpet
https://i.imgur.com/NJ2Gi3Mm.png