I personally use water lettuce in my 200G predator tank for a few reasons...
1) My puffer seems to enjoy the bits of shade the plant cover offers
2) It helps a little bit with keeping parameters in check, but only by a little (so in otherwords, nothing beats a large water change...
3) It helps keep my tank as a slightly lower light setup, since the only other plants in that tank are anubias...
If your looking to keep parameters in check through plants, i would look into using pythos instead, since that plant seems to grow so fast a lot of members here have had great results with using that in addition to their regular filtration...