In the 20G:
cabomba
green foxtail
java moss
bacopa carolina
amazon sword
some random floating things - duckweed??
dwarf lilly
anubias
water sprite or wysteria - not sure but it has grown alot recently
somethng german sounding - seaweed like thing
I had some others but they went all gooey
Giant hygro?
anacharis
pogo erectus
The foxtails, dwarf lilly and water sprite thing do the best. Amazon sword and anubias also do well. The bacopa carolina - i find it floating every day. I think my snails knock it out of the sand
I want something to carpet the bottom...but i need something that is easy and not a high light plant