Identify this plant.

[Truffs1178]

I found this growing out of the moist substrate in one of my invert tanks. I'm guessing its a foreign species. It's very young and looks like a mimosa that plant that when you touch folds up. Btw I used to grow mimosas so I know what they look like at this stage but I'm not 100% sure. It grows very fast and wasn't there a few days ago. It's probably too young to tell what it is.