I'll add into the chorus of 'yay pennywort!'. I have it in two tanks and the bettas love it. It grows easily, it's neater than a lot of floating plants, and it makes a great hammock for resting fish.
I also have the bacopa in three different tanks, all with different lighting situations. In my high light/CO2 tank, it's gorgeous with big leaves and a solid rate of growth. In my medium light tank, it's growing slower but with nice leaves. In the low light it's crawling, but healthy. It's a slower growing stem, which is nice compared to some that you have to trim twice a week in my high light tank. If you get it from a store, you may get the emersed form which has little leaves. It grows in bigger, lighter colored leaves that I love.
betta splendens (domestic) | betta imbellis | betta falx