well, I have floating plants that absorb some light and my tank is pretty dense. I have moneywort, rotala wallichi, Eleocharis parvula, Cabomba caroliniana, Egeria Densa, and ALOT of Alternanthera reineckii(I believe, not sure). The floating plants I have are water lettuce.
20G heavily planted tank with Eco Complete
Pressurized CO2, Eheim Ecco 2236, 1 55W and 1 36W bulb