I have a 40 gallon tank that I have been in the process of setting up. I ran it bare bottom for at least a month, because I could not find a substrate I liked. I started out with floating plants. Then I saw some ludwigia repens in plastic pot, and after reading how hardy it was, I bought it, hoping I could keep it temporarily in the plastic pot until I got my substrate in. In fact, I did this with two onion plants, and a cryptocoryne also. The onion plants and crypt were fine. The ludwigia repens started to rot at the base in about a week, so I cut the stem above the rotting area, threw out the pot, and floated the ludwigia. About a week later, I got my substrate in (inert 3M colorquartz, T grade), and yesterday I planted the ludwigia in the substrate, and added a couple of Flourish root tabs. I'm hoping the ludwigia will not rot. This is a no CO2, low-demand plants only, kind of tank. Does anyone know why the ludwigia rotted when it was in the pot, and do you think it will do better in the substrate? I am also using a low alternating dose of Flourish and Flourish Iron.