what the heck is this?

[Dondante]

I couldnt get a better pic. I couldn't get a pic of his top at all. He's smooth. Doesn't feel like it has a shell. When I touched it sort of shrunk a bit. Then straighten out and moved down the glass about 1/4 of an inch.

 

[cmcoker]

Perhaps a flatworm of some type, scroll down and take a look at some of the pics/links here:
http://chucksaddiction.thefishestate.net/hitchworms.html

 

[reef lover]

Polyclad. Remove him.

 

[Dondante]

Are they bad? Think there are more? What do they eat? More importantly is there anything that eats them?

 

[reef lover]

Polyclad...prey on lps...manual removal at night with red light is best. Dont think there's any natural predators...

 

[Oshengems]

Polyclad...prey on lps...manual removal at night with red light is best. Dont think there's any natural predators...

I think my springer damsel was eating them but I couldn’t tell you if it was a different kind of flatworm it looks very similar in color but more oval probably red planaria I’m not 100% sure

 

[Dondante]

Closest thing I could find

 

[Oshengems]

Closest thing I could find

Look up red planaria they look similar as well

 

[Mikedawg]

This might be helpful, especially fourth picture down: https://www.melevsreef.com/articles/acropora-eating-flat-worms-aefw
I would search R2R for Flatworm Exit which some reefers have successfully used to kill off these pests. Good luck