Weird vein-like plant growing up side of tank?

[FrogFever]

I found this vein like structure on the side of my tank one evening. I went back the next day and it had doubled its length overnight and traveled a great distance across the glass. It did the same thing by the next day. From what I can tell there is a piece of leaf touching the glass at the starting point. It looks like the veins literally grew off of the leaf and onto the glass and kept going
Any ideas?

[wesleybrouwer]

It's a slime mold.

[flybyferns]

FrogFever,
Additional information - see link: Vivaria Projects - plants

[Lady medusa]

Looks like a bryzoan to me but bryzoans are aquatic animals living in both fresh and marine water. It is very likely a fungus or mold.