floating plant question

is there a floating plant that doesn't require a light on the tank? my 50g does not have a light on it but i'd like to try to get some floaters in there if i can to help keep the water a bit cleaner and give my lung some added privacy. my lungfish likes to dig a lot so i can't put any decorations in his tank, plus he broke his last tank with a rock i put in there for him.:wall: so the only option i have for him are floaters, if that. maybe some duckweed? i heard this stuff grows like mad....what do you guys think? also, there are lots of lights in the room and the room gets a lot of sun light (but the tank doesn't get any direct sun light)...let me know. thanks.

thanks guys. i'm going to try to get some duckweed and some water lettuce and see how things work out. i got him some sand today so as soon as i can(hopefully tomorrow) i'll be cleaning that for him so he can bury himself a bit like he would in nature. and here's some lung pics for squeakfish, even though he didn't read my question before answering it...lol..
also b4 i get in 'crap' for keeping him in such a small tank i just want to say he had a bigger tank and he broke it, then i put him in a pond i made out of a pool and he didn't eat for 2 months. so back into the 50 he went and he is doing much better now. lung fish don't really swim anyways, just to go up to the top to breath, they like to bury themselves and conserve energy. anyways. pics:


on his way for a breath


in the pool before i added gravel


mmm...shrimp!


just chillin


hotdog treat

thanks. he got his new sand put in today. i'll try to get a pic if i can but i think my batteries are dead on the digi.