Yes, that's hornwort. You'll see a lot of differences in photos of that plant because it looks different a lot. The old growth is a dark avocado green like that. Under stronger lighting with a lot of new growth, it's a bright green color. If a lot of nutrients are present is grows bushy and thick like yours is. But if it's sucked up all the nutrients to a point of depletion, it begins to starve.. shedding needles and growing sparsely and straggly looking.. and it can actually die out completely for that lack of nutrients.
Hornwort can be a little temperamental like this, but it also serves as an excellent barometer you can use to see what's actually going on in the tank.