Hey sorry if this is in the wrong section of the plant forum but i just guessed were to post it.

I have been trying to keep Vallisneria americana for a long time but they have only lasted a few weeks before turning brown and dies i wasn't planing to keep these but when i picked up my fish from my uncle he threw a few in since he had to much of them. They are growing fine in my 30 gallon tank but in the 100 they keep dieing.

The 100 gallon has a powerglo and a aquaglo fluorescent lights T8 i think. (says t8 on the package i got them in)
I only use the aquaclo for lightning the powerglo is always turned off looks alot cleaner and nicer with only the aquaglo on.

The 30 gallon has just normal fluorescent lights you buy for next to nothing no aquarium lights at all just normal household lights.

I don't use any fertilizer apart from the fish no need for more atleast in the old days so why need it now.