Since the leaves appear to be white on the bott oyl m its def not anacharis. My guess would be a rotala. not sure which though. Maybe a bacopa. What seller did u buy from? You might be able to find it on their site
Okay I'll admit that they were guesses as to what it actually is but I can tell u with 100 percent certainty it has way too opaque of leaves to be anything like elodea or egeria. I've had those pretty much since I started keeping fish and the leaves are never rounded at the end like these and the bottom is never lighter than the top. This plant is a stem, but it's not elodea or egeriaCome on - it isn't even close to bacopa or rotala. Also the leaves aren't 'white' on the bottom.