Hi
Java Fern is an excellent low light plant for GF tanks (most GF won't eat it for one thing!) and many of the Cryptocoryne family also do well. Elodea is another one, though that may get chomped on, and Anacharis *can* grow in low light (though it prefers medium lighting). Hornwort also will cope with low light though you may not see much new growth.
Hope this helps.