Bert, I have water with kh of 12-15 and also live over a limestone aquifer in san antonio. I agree with your points and have found them all to be true to some degree. esp the stunting. in fact i have some l. senegalensis that 'adapted' to this water and the color is great but the leaves are about half their normal size. its going to the for sale section soon cause i cant deal with a plant not reaching its potential in my tanks. running the tank lean i have found is not a good idea. i tried this in my 2.5 to attempt to bring out the orange in my l. brevipes and algae started taking hold-green dust. since i started dosing more growth is better but no more orange ludwigia. anyways good observations here always learning something here.