What the heck are these things??

[Fishy Newbie]

Recently these 2 UFOs appeared in our Fluval Flex and are unwelcome. The white critters live on the driftwood and are boring holes into one of the nerite's shell. The pinkish critters have arms (?) that wave in the water current and seem to be stationary on the glass.
If anyone knows what these things are, if they are related and how we can get rid of them, any help or advice would be appreciated. Besides, they're CREEPY!! Thanks.

 

[Back in the fold]

Hydra and seed shrimp would be my guess.