I think you should plant the tank. Just take whatever household plant you've got just laying about, pointsettas, banana trees, a royal pine. It'll give your tank a more natural habitat type of feel.
OMG.... someone did NOT mention adding a neon tetra to that tank. What a nightmare that little bugger can be, PLUS it'd be a sin to put him in a tank so small! And PLEASE don't say they are happier in groups... I found the opposite to be the truth.