Anacharis dying

I've got a small 1 gal tank set up for the Betta I plan to get shortly. I've
been doing "fishless cycling" using ammonia and, once the cycling process
was nearly complete, I added a few plants: some bacopa, some anacharis, and
some java moss. Everything was put in just before I went on a week-long
business trip to Japan (with the idea that the tank would be ready for a
Betta when I got back).

I've got a small "bubble" filter in the tank and a heater. There's about a
half inch of gravel on the bottom. Water temperature is 80 degrees.
Illumination is a 15 watt compact fluorescent lamp. Tested water today and
got pH 6.8, Ammonia 0 ppm, Nitrites 0 ppm, and Nitrates 80 ppm. (Looks like
the cycling is done).

Well, the bacopa and java moss are doing fine. Both have grown noticeably
since I've been gone. The anacharis, however, isn't doing well at all. The
leaves have gone wan and transparent and the stems have gone very soft and
broken in spots (leaving some stems floating in the water). I've pulled out
what's left although I haven't gravel vacced yet.

Any idea why my Anacharis is dying? Any suggestions on some other plant
choices for a small Betta tank?

--
David L. Burkhead "Dum Vivimus Vivamus"
"While we live, let us live."
My webcomic Cold Servings
http://www.coldservings.com -- Back from hiatus!
Updates Wednesdays