Nice lil tank you got there, buddy

If I didn't know better, I would think that was a bigger tank; maybe a 10-gal or 15!
If anything, I think the sharp contrast in height bet. HC and hairgrass would make the scene all the more interesting. One thing about small tanks is to try to keep things simple. You can perhaps add some
Crypt parva or
Anubias nana petite here and there as accents to give it a finished touch. Otherwise, I really don't see any problem with using HC in the foreground.