I've asked a few questions like this and lots of people seem to prefer brazillian pennywort. I had it before and liked it alot but i got rid of it because i had a bad algae issue and it got on the plant and made the tank look bad. Theres also frogbit (apparently it is a nuisance), water sprite, wisteria, and probably alot more that i dont know of. Im sure someothers will give some input!