Marty: I have had the same problem with Java Fern dying off in several, but not all of my tanks. I notice a seasonal cycle: it happens in late spring/early summer. There are no other correlations that I can discern. It never happens to the "Tropica" variety, even if it is in the same tank as the other species that are dying off. Very puzzling. - Jack O'Leary -- Ask not what your village can do for you ...