What Is This?

[MicG]

Found this outside my main tank.
It moves by bowing and stretching, one side will lift up and explore. It has small legs on two sides near the ends.
I don’t know what but it is, but does it have something to do with the aquarium?

 

[Coptapia]

An Inchworm, the caterpillar of a Geometer Moth.

 

[Fishcat]

They sometimes come inside on clothing or hair, as they are often found dangling from trees. One of several reasons why I wear a hat outdoors.