Any ideas?

[Trekka]

Just happened to find these tinies on the glass near the top of our 55 reef tank. Took a pic with my thumb in there for a general size comparison. I'm a little lost on this one.

 

[Trekka]

Hydroids? Where would they have come from? We haven't added anything to the tank and it's been established for a year.

 

[EeyoreIsMySpiritAnimal]

They just happen. They will go away on their own.

 

[bushdoc]

They have been somwhere there hiding, perhaps in a sump. Those looks like medusa stage of hydroid.