Water Lettuce can survive soooo much.
I had a baby pike (an inch long) for a month, so I scooped up some filthy pond water with TONS of tiny organisms, tossed in a giant ball of algae, a big scoop of water lettuce, and used the organisms to feed the pike.
I didn't even keep the bucket in the light, it just stayed in the shade on the back deck for maybe 4 months after I gave the pike back to my friend (don't ask lol) and I totally forgot about it...
A few weeks ago I decided to dump the bucket, and I found that the water lettuce was a brilliant green and it had completely overtaken the 5 gallon bucket. I threw it out anyway because there were so many possibly fish-dangerous organisms in there.
So yeah, water lettuce is easy to care for.