I have a 10L setup and one of those clip on 9w lamps.
I am growing these plants below successfully with that light and co2 injection
Alternanthera reineckii Bacopa monnieri Limnobium laevigatum
Java Moss
Tonnina Some kind of Hygrophila plant (from amazon, purple)
Windelow Moss (?) or something that looks very much like it.
Why not try dwarf hair grass? It says "ANY" light is okay.