What is this plant?

[KayBray]

These plants came with my crystal red shrimp. I planted them in my substrate and they are thriving -- I thought they were hornwort but after looking at pictures, I can see they are not. Anyone know?

 

[Byron]

It looks like Heteranthera zosterifolia, common name Stargrass (for obvious reason). More here:
http://www.aquaticplantcentral.com/forumapc/plantfinder/details.php?id=67

Google photos and you will see it can vary like most plants in leaf blade size depending upon growing conditions. It culd be something else, but this plant came to mind when I saw your photo.

Byron.