i've got a pretty well established java fern in my tank and it's started to have a bit of a problem. I recently added some aqua soil and and some laterite to my tank and since i did this the tips of some leaves look like they are burned.
20 gal tall freshwater glass tank Set up: Aquaclear Power Filter with BioMax (30 gal), Current USA 65W PC lighting 10k/6700. Heavily planted (Limnophila hippuroides, moneywort, common frill, anubias, wisteria (Hygrophila difformis), amazon sword, red temple (Alternanthera reineckii), red ludwigia (repens), narrow leaf chain sword, purple cabomba, red tiger lotus, four leaf clover, dwarf baby tears), and Marble Queen Radican sword, with cliffstone, riverstone, driftwood, black flourite substrate
Occupants: Angelfish, yoyo loach, otocinculs, Red Wag Platy
10gal freshwater Setup: Aquaclear Powerfilter with Biomax (20 gal)
Planted: Common frill, wisteria, guppy grass, java moss
Occupants: Indian Dwarf Puffer
3 gal Freshwater
guppy grass and java moss
Occupants: Snowball shrimp
Down to 1 planted 10g w/
1 Male Betta
2 Julii Cory
3 Emerald Cory
3 Long-Finned Blue Danios
5 Neon Tetras
Posts: 17
My Java Ferns blackened and made me worry, same as you. However, after two months, each leaf that blackened sprouted new leaves and I found little sprouts floating all over the tank, stuck in the java moss.