If you do put floating bog type plants in I would recommend hyacinth or frogbit. But the key is harvesting them as they get bigger and keep the smaller new growth in there. You would be amazed how much crud those roots collect. But they will get long, and go to places you don't want them and overcrowd if you do not harvest often. Both types will send off multiple runners. Snap the runners off and toss the mother plant. Nice set up, I'm working on something similar but a bit larger scope.
