So I have an interesting problem with frogbit and water lettuce. For some reason in my 5 gallon tank these plants like to grow roots as long as 2 feet. Now I don't mind a few roots hanigng down but every 2 or 3 weeks i have to pull a lot of them out because the roots create a complete barrier in the tank preventing the fishes from swimming. Why are they growing such long roots ? Is there a way to train them to limit their roots to 8 inch or so ?