I bought a couple of plants in recent weeks (after searching high and low) and they have never looked back in NYC soft water with Flourite, CO2, NO3 and PO4 additions. They seem to be tolerant.
Plant finder:
http://www.aquaticplantcentral.com/forum/plant_data/details.php?id=108
Andrew Cribb
Plant finder:
http://www.aquaticplantcentral.com/forum/plant_data/details.php?id=108
Andrew Cribb