Hello,
My parameters are very close to yours. I do grow Vallisneria americana
in my excel tanks and they do well. Other plants that I have had success with are:
Aponogeton boivinianus
Anubias barteri v. 'nana'
Bacopa caroliniana
Cryptocoryne wendtii
Ludwigia repens
Sagittaria subulata
Echinodorus x barthii
Tonina fluvitalis
Please let us know how you do with your excel tank.
It is said that valisneris will adapt to Excel if you slowly increase the amount that you dose. I can't verify this firsthand, but since vals is so cheap it couldn't hurt to try.