I will definitely have to look into the brazilian pennywort. I love the way it's creeps. Your outside aquarium looks so happy! When it warms back up here I would love to try taking some of my plants outside for some true sun.
I may have some extra pennywort by the time it's Spring, I may be able to send you some just for the cost of shipping.
The tub is essentially where I throw all my extra plants, I like them and they seem to like the sun so it works out. :P