Help me ID this worm please

[Pom Herder]

These creatures started showing up all over my glass. They are about 1 inch long, maybe 1/32 inch wide. They attach to the tank glass at their base and their skinny body waves around in the current. They have about 7 fingers moving around at the base. Are they harmful?

 

[KJ]

These creatures started showing up all over my glass. They are about 1 inch long, maybe 1/32 inch wide. They attach to the tank glass at their base and their skinny body waves around in the current. They have about 7 fingers moving around at the base. Are they harmful?

Synaptidae (Cucumber) good CUC.

 

[Lovemyreef2015]

Synaptidae (Cucumber) good CUC.

Agree^^

 

[sfin52]

I'll got with @Lovemyreef2015 and @KJ.

 

[Pom Herder]

Thanks to all for the helpful responses; I feel relieved. Anyone know how big these things get?