Worm pest identification

[ScubaZ]

I passed by my tank when the lights were off and noticed these worm like things on the glass. I removed from what I can see but sure there’s plenty more. I do not know what they are or if they are harmful to my coral any information would be greatly appreciated. Thanks

 

[Crabs McJones]

Serolid isopod. Good find :)

 

[Dierks]

Looks like some Sea Cradle... Google that and see if its what it is... They are good guys if it is